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/Kconfig b/fs/Kconfig
index e6803ac..1cb9831 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -4,6 +4,8 @@
 
 menu "File systems"
 
+source "fs/btrfs/Kconfig"
+
 source "fs/cbfs/Kconfig"
 
 source "fs/ext4/Kconfig"