gfs2: Fix the crc32c dependency

Depend on LIBCRC32C which uses the crypto API to select the appropriate
crc32c implementation.  With the CRYPTO and CRYPTO_CRC32C dependencies,
gfs2 would still need to use the crypto API directly like ext4 and btrfs
do, which isn't necessary.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>