fs: export fs_close()

fs_close() closes the connection to a file system which opened with
either fs_set_blk_dev() or fs_set_dev_with_part(). Many file system
functions implicitly call fs_close(), e.g. fs_closedir(), fs_exist(),
fs_ln(), fs_ls(), fs_mkdir(), fs_read(), fs_size(), fs_write()
and fs_unlink().
So just export it.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/include/fs.h b/include/fs.h
index 7601b03..5a1244d 100644
--- a/include/fs.h
+++ b/include/fs.h
@@ -38,6 +38,13 @@
 int fs_set_blk_dev_with_part(struct blk_desc *desc, int part);
 
 /**
+ * fs_close() - Unset current block device and partition
+ *
+ * Should be paired with either fs_set_blk_dev() or fs_set_dev_with_part()
+ */
+void fs_close(void);
+
+/**
  * fs_get_type_name() - Get type of current filesystem
  *
  * Return: Pointer to filesystem name