mimxrt: Fix the UART.deinit() and uart_deinit_all() behaviour.

The code did not check at deinit whether a UART was initialized.
That did not matter for all MCU's except MIMXRT1176, which crashes
at the second soft reset in a row.

But since it is a general problem to use UART methods of a UART
which has been deinitialized, checks were added to all methods for a
clear response instead of e.g. a crash.

Signed-off-by: robert-hh <robert@hammelrath.com>

ports/mimxrt/machine_uart.c

@@ -81,6 +81,7 @@ static const iomux_table_t iomux_table_uart[] = {
 static const iomux_table_t iomux_table_uart_cts_rts[] = {
     IOMUX_TABLE_UART_CTS_RTS
 };
+static bool uart_active[MICROPY_HW_UART_NUM];
 
 STATIC const char *_parity_name[] = {"None", "", "0", "1"};  // Is defined as 0, 2, 3
 STATIC const char *_invert_name[] = {"None", "INV_TX", "INV_RX", "INV_TX|INV_RX"};
@@ -306,6 +307,7 @@ STATIC mp_obj_t machine_uart_init_helper(machine_uart_obj_t *self, size_t n_args
         self->lpuart->STAT |= 1 << LPUART_STAT_BRK13_SHIFT;
         LPUART_EnableTx(self->lpuart, true);
     }
+    uart_active[self->id] = true;
 
     return MP_OBJ_FROM_PTR(self);
 }
@@ -351,7 +353,10 @@ MP_DEFINE_CONST_FUN_OBJ_KW(machine_uart_init_obj, 1, machine_uart_init);
 // uart.deinit()
 STATIC mp_obj_t machine_uart_deinit(mp_obj_t self_in) {
     machine_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    LPUART_Deinit(self->lpuart);
+    if (uart_active[self->id]) {
+        LPUART_Deinit(self->lpuart);
+    }
+    uart_active[self->id] = false;
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_uart_deinit_obj, machine_uart_deinit);
@@ -384,9 +389,10 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_uart_txdone_obj, machine_uart_txdone);
 
 // Deinitialize all defined UARTs
 void machine_uart_deinit_all(void) {
-    for (int i = 0; i < sizeof(uart_index_table); i++) {
-        if (uart_index_table[i] != 0) {
+    for (int i = 0; i < MICROPY_HW_UART_NUM; i++) {
+        if (uart_index_table[i] != 0 && uart_active[i] == true) {
             LPUART_Deinit(uart_base_ptr_table[uart_index_table[i]]);
+            uart_active[i] = false;
         }
     }
 }