this fixes coverity id #489.

Since the last element in the array is always ARRAY_SIZE-1 we have to check
for ipcnum >= ARRAY_SIZE()
Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>