tcl/target/ti_k3: Add AXI-AP port for direct SoC memory map access

While we can read and write from memory from the view of various
processors, all K3 debug systems have a AXI Access port that allows
us to directly access memory from debug interface. This port is
especially useful in the following scenarios:

1. Debug cache related behavior on processors as this provides a
   direct bypass path.
2. Processor has crashed or inaccessible for some reason (low power
   state etc.)
3. Scenarios prior to the processor getting active.
4. Debug MMU or address translation issues (example: TI's Region
   Address Table {RAT} translation table used to physically map
   SoC address space into R5/M4F processor address space)

The AXI-AP port is the same for all processors in TI's K3 family.

To prevent a circular-loop scenario for axi-ap accessing debug memory
with dmem (direct memory access debug), enable this only when dmem is
disabled.

Change-Id: Ie4ca9222f034ffc2fa669fb5124a5f8e37b65e3b
Reported-by: Dubravko Srsan <dubravko.srsan@dolotron.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7899
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins

tcl/target/ti_k3.cfg

@@ -417,4 +417,7 @@ if { 0 == [string compare [adapter name] dmem ] } {
 	} else {
 		puts "ERROR: ${SOC} data is missing to support dmem access!"
 	}
+} else {
+	# AXI AP access port for SoC address map
+	target create $_CHIPNAME.axi_ap mem_ap -dap $_CHIPNAME.dap -ap-num 2
 }