cciss: fix build when !PROC_FS

Fix these build errors when CONFIG_PROC_FS is not set:
drivers/block/cciss.c: In function 'cciss_show_raid_level':
drivers/block/cciss.c:623: error: 'RAID_UNKNOWN' undeclared (first use in this function)
drivers/block/cciss.c:626: error: 'raid_label' undeclared (first use in this function)
drivers/block/cciss.c: In function 'cciss_geometry_inquiry':
drivers/block/cciss.c:2696: error: 'RAID_UNKNOWN' undeclared (first use in this function)

Signed-off-by: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>