spl: fix ext4fs_mount return code handling

- Despite other ext4 filesystem functions, ext4fs_mount returns
  0 in case of error.
- This leads to u-boot crash in case that an SD card
  with valid partition table but without ext4 filesystem created
  in a partition is found on SD card.
- Fix this by returning a proper error code of '-1' from spl_load_image_ext
  function in case of ext4fs_mount error.

Signed-off-by: Thomas Schaefer <thomas.schaefer@kontron.com>
[hthiery: slightly reword the commit message]
Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

common/spl/spl_ext.c

@@ -32,7 +32,7 @@ int spl_load_image_ext(struct spl_image_info *spl_image,
 #ifdef CONFIG_SPL_LIBCOMMON_SUPPORT
 		printf("%s: ext4fs mount err - %d\n", __func__, err);
 #endif
-		goto end;
+		return -1;
 	}
 
 	err = ext4fs_open(filename, &filelen);