arch/arm/src/imxrt/imxrt_idle.c: Y'all remember that conversation we had about why WFI might have been disabled on imxrt? Well, looks like we found the reason;

https://github.com/zephyrproject-rtos/zephyr/pull/8535/commits:  "The imxrt1050 is configured to use SYSTICK for the kernel timer, but SYSTICK cannot wake up the soc from low-power modes. Disable low-power modes on this soc until we have support for an alternative timer."

    "This fixes k_sleep on the EVKB version of the mimxrt1050_evk board. An earlier version of the board (EVK, not EVKB), had A0 silicon which by default did not enter low-power mode on a wfi."

This patch reverts the WFI enable for further investigation post 8.2.  With this patch in place together with the previous one my system is fully stable(*), just drinking a bit more power than I'd like.

arch/arm/src/imxrt/imxrt_idle.c

@@ -177,7 +177,15 @@ void up_idle(void)
 
   up_idlepm();
 
-#if 1
+/* This code is disabled due to fact CPU cannot recover from low
+ * power mode via SYSTICK according to:
+ *
+ *   https://github.com/zephyrproject-rtos/zephyr/pull/8535/commits
+ *
+ * For further investigation post release of 8.2.
+ */
+
+#if 0
   /* Sleep until an interrupt occurs to save power. */
 
   BEGIN_IDLE();