common: Move functions for loading from fat/ext2 to fs.h

These are filesystem functions and belong in the filesystem header file.
Move them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/inversepath/usbarmory/usbarmory.c b/board/inversepath/usbarmory/usbarmory.c
index 1951018..e9eea40 100644
--- a/board/inversepath/usbarmory/usbarmory.c
+++ b/board/inversepath/usbarmory/usbarmory.c
@@ -9,6 +9,7 @@
 
 #include <common.h>
 #include <command.h>
+#include <fs.h>
 #include <asm/io.h>
 #include <asm/arch/imx-regs.h>
 #include <asm/arch/sys_proto.h>