[PATCH v8 1/2] efi: Introduce efi_memdesc_ptr to get pointer to memmap descriptor

The existing map iteration helper for_each_efi_memory_desc_in_map can only be used after OS initializes EFI to fill data of struct efi_memory_map. Before that we also need iterate map descriptors which are stored in several intermediate structures, like struct efi_boot_memmap for arch independent

[PATCH v8 1/2] efi: Introduce efi_memdesc_ptr to get pointer to memmap descriptor

The existing map iteration helper for_each_efi_memory_desc_in_map can only be used after OS initializes EFI to fill data of struct efi_memory_map. Before that we also need iterate map descriptors which are stored in several intermediate structures, like struct efi_boot_memmap for arch independent