[PATCH] drivers/block/acsi_slm.c: size_t can't be < 0

A size_t can't be < 0.

(akpm: and rw_verify_area() already did that check)

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>