btrfs: add blk_types.h include to compression.h

When moving the printk messages into their own file I got a compiler
error because the includes grabbed compression.h, but nothing pulled in
the blk_types.h dependency that compression.h has because it uses
blkstatus_t.  Add blk_types.h to compression.h so that this sort of
thing doesn't happen in the future.
Reviewed-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/compression.h

@@ -6,6 +6,7 @@
 #ifndef BTRFS_COMPRESSION_H
 #define BTRFS_COMPRESSION_H
 
+#include <linux/blk_types.h>
 #include <linux/sizes.h>
 
 struct btrfs_inode;