Coverity found an over-run @ line 364 of efi.c

This is due to the loop checking the size correctly, then adding a '\0'
after possibly hitting the end of the array.

Ensure the loop exits with one space left in the array.
Signed-off-by: Darren Jenkins <darrenrjenkins@gmail.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>