Move all code paths touched by NMI to IRAM

Prerequisite for calling Cache_Read_Disable() for OTA updates.

Massive thanks due to @foogod and their xtobjdis tool, creating the call
graph of where the wDev_ProcessFiq touched (including in newlib, etc.)
would have otherwise been very painful:
https://bitbucket.org/foogod/xtobjdis

core/newlib_syscalls.c

@@ -7,9 +7,10 @@
 #include <sys/reent.h>
 #include <sys/types.h>
 #include <espressif/sdk_private.h>
+#include <common_macros.h>
 #include <stdlib.h>
 
-caddr_t _sbrk_r (struct _reent *r, int incr)
+IRAM caddr_t _sbrk_r (struct _reent *r, int incr)
 {
     extern char   _heap_start; /* linker script defined */
     static char * heap_end;

core/sdk_compat.c

@@ -8,8 +8,9 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
+#include <common_macros.h>
 
-void *zalloc(size_t nbytes)
+void IRAM *zalloc(size_t nbytes)
 {
     return calloc(1, nbytes);
 }