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_ext4.c b/common/cmd_ext4.c
index ca46561..237bc19 100644
--- a/common/cmd_ext4.c
+++ b/common/cmd_ext4.c
@@ -47,10 +47,10 @@
 #include <image.h>
 #include <linux/ctype.h>
 #include <asm/byteorder.h>
-#include <ext_common.h>
 #include <ext4fs.h>
 #include <linux/stat.h>
 #include <malloc.h>
+#include <fs.h>
 
 #if defined(CONFIG_CMD_USB) && defined(CONFIG_USB_STORAGE)
 #include <usb.h>
@@ -59,18 +59,12 @@
 int do_ext4_load(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);
 }
 
 int do_ext4_ls(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);
 }
 
 #if defined(CONFIG_CMD_EXT4_WRITE)