Change the signature value

The existing value 0x6e_d0ff has 0xff in its bytes, which is not ideal
since this is a common value in memory.

Use 0x40_b10b instead, intended to mean handoff blobs.

Let the bike-shedding begin.

Signed-off-by: Simon Glass <sjg@chromium.org>

source/register_conventions.rst

@@ -55,7 +55,7 @@ absent from the transfer list.
    +--------------+-------------------------------------------------------------+
    | X1           | X1 is divided into the following fields:                    |
    |              |                                                             |
-   |              | - X1[23:0]: set to the TL signature (0x6e_d0ff)             |
+   |              | - X1[23:0]: set to the TL signature (0x40_b10b)             |
    |              | - X1[31:24]: version of the register convention used. Set to|
    |              |   1 for the AArch64 convention specified in this document.  |
    |              | - X1[63:32]: reserved, must be zero.                        |
@@ -101,7 +101,7 @@ absent from the transfer list.
    +--------------+-------------------------------------------------------------+
    | R1           | R1 is divided into the following fields:                    |
    |              |                                                             |
-   |              | - R1[23:0]: set to the TL signature (0x6e_d0ff)             |
+   |              | - R1[23:0]: set to the TL signature (0x40_b10b)             |
    |              | - X1[31:24]: version of the register convention used. Set to|
    |              |   1 for the AArch32 convention specified in this document.  |
    |              |                                                             |

source/transfer_list.rst

@@ -48,7 +48,8 @@ Transfer list header
 
 A TL must begin with a TL header. The layout of the TL header is shown in
 :numref:`tab_tl_header`.  The presence of a TL header can be verified by
-inspecting the signature field which must contain the 0x6e_d0ff value.  The
+inspecting the signature field which must contain the 0x40_b10b value.  The
+
 version field determines the contents of the handoff start header. The version
 will only be changed by an update to this specification when new TL header or
 TE header fields are defined (i.e. not when allocating new tag IDs), and all
@@ -66,7 +67,7 @@ changes will be backwards-compatible to older readers.
    * - signature
      - 0x4
      - 0x0
-     - The value of signature must be `0x6e_d0ff`.
+     - The value of signature must be `0x40_b10b`.
 
    * - checksum
      - 0x1
@@ -198,7 +199,7 @@ Inputs:
 
 - `tl_base_addr`: Base address of the existing TL.
 
-#. Compare `tl.signature` (`tl_base_addr + 0x0`) to `0x6e_d0ff`. On a mismatch,
+#. Compare `tl.signature` (`tl_base_addr + 0x0`) to `0x40_b10b`. On a mismatch,
    abort (this is not a valid TL).
 
 #. Compare `tl.version` (`tl_base_addr + 0x5`) to the expected version
@@ -353,7 +354,7 @@ Inputs:
 
 #. Check that `available_size` is larger than `0x18` (the assumed `tl.hdr_size`), otherwise abort.
 
-#. Set `tl.signature` (`tl_base_addr + 0x0`) to `0x6e_d0ff`.
+#. Set `tl.signature` (`tl_base_addr + 0x0`) to `0x40_b10b`.
 
 #. Set `tl.checksum` (`tl_base_addr + 0x4`) to `0x0` (for now).