fix oops on rmmod capidrv

Fix overwriting the stack with the version string
(it is currently 10 bytes + zero) when unloading the
capidrv module. Safeguard against overwriting it
should the version string grow in the future.

Should fix Kernel Bug Tracker Bug 9696.

Signed-off-by: Gerd v. Egidy <gerd.von.egidy@intra2net.com>
Acked-by: Karsten Keil <kkeil@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>