efi/capsule-loader: fix incorrect allocation size

gcc-14 notices that the allocation with sizeof(void) on 32-bit architectures
is not enough for a 64-bit phys_addr_t:

drivers/firmware/efi/capsule-loader.c: In function 'efi_capsule_open':
drivers/firmware/efi/capsule-loader.c:295:24: error: allocation of insufficient size '4' for type 'phys_addr_t' {aka 'long long unsigned int'} with size '8' [-Werror=alloc-size]
  295 |         cap_info->phys = kzalloc(sizeof(void *), GFP_KERNEL);
      |                        ^

Use the correct type instead here.

Fixes: f24c4d47 ("efi/capsule-loader: Reinstate virtual capsule mapping")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>