efi: memmap: fix kernel-doc warnings

Correct all kernel-doc notation to repair warnings that are
reported by scripts/kernel-doc:

memmap.c:38: warning: No description found for return value of '__efi_memmap_init'
memmap.c:82: warning: No description found for return value of 'efi_memmap_init_early'
memmap.c:132: warning: Function parameter or member 'addr' not described in 'efi_memmap_init_late'
memmap.c:132: warning: Excess function parameter 'phys_addr' description in 'efi_memmap_init_late'
memmap.c:132: warning: No description found for return value of 'efi_memmap_init_late'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-efi@vger.kernel.org
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>