efi: Fix compiler warnings

efi: Fix compiler warnings

This occur when building on Raspberry Pi 400 (32-bit ARM). Fix them.

Examples:

cmd/efidebug.c: In function ‘do_efi_capsule_update’:
cmd/efidebug.c:75:49: warning: cast from pointer to integer of different
	size [-Wpointer-to-int-cast]
  ret = EFI_CALL(RT->update_capsule(&capsule, 1, (u64)NULL));
                                                 ^
include/efi_loader.h:104:9: note: in definition of macro ‘EFI_CALL’
  typeof(exp) _r = exp; \
         ^~~
cmd/efidebug.c:75:49: warning: cast from pointer to integer of different
	size [-Wpointer-to-int-cast]
  ret = EFI_CALL(RT->update_capsule(&capsule, 1, (u64)NULL));
                                                 ^
include/efi_loader.h:104:19: note: in definition of macro ‘EFI_CALL’
  typeof(exp) _r = exp; \
                   ^~~

In file included from include/common.h:20,
                 from lib/efi_loader/efi_capsule.c:9:
lib/efi_loader/efi_capsule.c: In function ‘efi_update_capsule’:
include/efi_loader.h:83:8: warning: format ‘%lu’ expects argument of type
	‘long unsigned int’, but argument 10 has type ‘size_t’
	{aka ‘unsigned int’} [-Wformat=]
  debug("%sEFI: Entry %s(" format ")\n", __efi_nesting_inc(), \
        ^~~~~~~~~~~~~~~~~~
include/linux/printk.h:37:21: note: in definition of macro ‘pr_fmt’
 #define pr_fmt(fmt) fmt
                     ^~~
include/log.h:229:2: note: in expansion of macro ‘log’
  log(LOG_CATEGORY, LOGL_DEBUG, fmt, ##args); \
  ^~~
include/log.h:249:2: note: in expansion of macro ‘debug_cond’
  debug_cond(_DEBUG, fmt, ##args)
  ^~~~~~~~~~
include/efi_loader.h:83:2: note: in expansion of macro ‘debug’
  debug("%sEFI: Entry %s(" format ")\n", __efi_nesting_inc(), \
  ^~~~~
lib/efi_loader/efi_capsule.c:444:2: note: in expansion of macro ‘EFI_ENTRY’
  EFI_ENTRY("%p, %lu, %llu\n", capsule_header_array, capsule_count,
  ^~~~~~~~~
lib/efi_loader/efi_capsule.c:444:19: note: format string is defined here
  EFI_ENTRY("%p, %lu, %llu\n", capsule_header_array, capsule_count,
                 ~~^
                 %u

Signed-off-by: Simon Glass <sjg@chromium.org>
Replace (uintptr_t)NULL by 0.
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>