bcache: bch_gc_thread() is not freezable

bch_gc_thread() doesn't mark itself freezable, so calling try_to_freeze()
in its context is just an expensive no-op.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/md/bcache/btree.c

@@ -27,7 +27,6 @@
 
 #include <linux/slab.h>
 #include <linux/bitops.h>
-#include <linux/freezer.h>
 #include <linux/hash.h>
 #include <linux/kthread.h>
 #include <linux/prefetch.h>
@@ -1787,7 +1786,6 @@ again:
 
 		mutex_unlock(&c->bucket_lock);
 
-		try_to_freeze();
 		schedule();
 	}