fs: btrfs: Add U-Boot fs handlers.

Signed-off-by: Marek Behun <marek.behun@nic.cz>

 create mode 100644 fs/btrfs/Kconfig
 create mode 100644 fs/btrfs/Makefile
 create mode 100644 fs/btrfs/btrfs.c
 create mode 100644 include/btrfs.h
diff --git a/fs/Makefile b/fs/Makefile
index b53c9d7..8a8175b 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -12,6 +12,7 @@
 else
 obj-y				+= fs.o
 
+obj-$(CONFIG_FS_BTRFS) += btrfs/
 obj-$(CONFIG_FS_CBFS) += cbfs/
 obj-$(CONFIG_CMD_CRAMFS) += cramfs/
 obj-$(CONFIG_FS_EXT4) += ext4/