docsrc: fix crc32hash type

Fix differing signedness warning:

Documentation/pcmcia/crc32hash.c:29: warning: pointer targets in passing argument 1 of 'crc32' differ in signedness

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>