[PATCH] Add missing overflow check in get_blkdev_list

Patch to clean up missing overflow check in get_blkdev_list.  The printf
which adds the "Block Devices" string in /proc/devices can overflow the
presented page if get_chrdev_list eats up the entire 4k space.

Signed-off-by: Neil Horman <nhorman@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>