MAINTAINERS: Add btrfs mailing list and myself as reviewer

Since the current code base is mostly from btrfs-progs, anyone
contributing to U-Boot btrfs code could also help us to improve
btrfs-progs and btrfs kernel module.

Also add myself as designated reviewer.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Marek BehĂșn <marek.behun@nic.cz>
diff --git a/MAINTAINERS b/MAINTAINERS
index 101f4e1..332112f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -599,6 +599,8 @@
 
 BTRFS
 M:	Marek Behun <marek.behun@nic.cz>
+R:	Qu Wenruo <wqu@suse.com>
+L:	linux-btrfs@vger.kernel.org
 S:	Maintained
 F:	cmd/btrfs.c
 F:	fs/btrfs/