zephyr/main: Put GC heap in noinit linker area.

By putting the heap in the noinit area instead of the bss area, zephyr
won't memset it to zero during start.  This improves startup time, in
particular if the heap is very big.  The system heap of zephyr is also in
the same section.

Signed-off-by: Fin Maaß <f.maass@vogl-electronic.com>

Author: maass-hamburg

ports/zephyr/main.c

@@ -83,7 +83,7 @@ DT_FOREACH_STATUS_OKAY(micropython_heap, MICROPY_HEAP_DEFINE)
 #include "modmachine.h"
 #include "modzephyr.h"
 
-static char heap[MICROPY_HEAP_SIZE];
+static __noinit char heap[MICROPY_HEAP_SIZE];
 
 #if defined(CONFIG_USB_DEVICE_STACK_NEXT)
 extern int mp_usbd_init(void);