fs: add filesystem switch libary, implement ls and fsload commands

Implement "ls" and "fsload" commands that act like {fat,ext2}{ls,load},
and transparently handle either file-system. This scheme could easily be
extended to other filesystem types; I only didn't do it for zfs because
I don't have any filesystems of that type to test with.

Replace the implementation of {fat,ext[24]}{ls,load} with this new code
too.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
diff --git a/common/cmd_ext2.c b/common/cmd_ext2.c
index c27d9c7..06d0234 100644
--- a/common/cmd_ext2.c
+++ b/common/cmd_ext2.c
@@ -37,15 +37,11 @@
 /*
  * Ext2fs support
  */
-#include <common.h>
-#include <ext_common.h>
+#include <fs.h>
 
 int do_ext2ls (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
-	if (do_ext_ls(cmdtp, flag, argc, argv))
-		return -1;
-
-	return 0;
+	return do_ls(cmdtp, flag, argc, argv, FS_TYPE_EXT);
 }
 
 /******************************************************************************
@@ -53,10 +49,7 @@
  */
 int do_ext2load (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
-	if (do_ext_load(cmdtp, flag, argc, argv))
-		return -1;
-
-	return 0;
+	return do_fsload(cmdtp, flag, argc, argv, FS_TYPE_EXT);
 }
 
 U_BOOT_CMD(