afs: remove unused variable 'afs_voltypes'

fs/afs/volume.c:15:26: warning:
 afs_voltypes defined but not used [-Wunused-const-variable=]

It is not used since commit d2ddc776 ("afs: Overhaul
volume and server record caching and fileserver rotation")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/volume.c

@@ -12,8 +12,6 @@
 unsigned __read_mostly afs_volume_gc_delay = 10;
 unsigned __read_mostly afs_volume_record_life = 60 * 60;
 
-static const char *const afs_voltypes[] = { "R/W", "R/O", "BAK" };
-
 /*
  * Allocate a volume record and load it up from a vldb record.
  */