drivers: fix typo in firmware/efi/memmap.c

[ Commit 1df4d172

 upstream ]

This patch fixes the spelling error in firmware/efi/memmap.c, changing
it to the correct word.

Signed-off-by: Zheng Zhi Yuan <kevinjone25@g.ncu.edu.tw>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>