spl: Add a name to the SPL load-image methods

It is useful to name each method so that we can print out this name when
using the method. Currently this happens using a separate function. In
preparation for unifying this, add a name to each method.

The name is only available if we have libcommon support (i.e can use
printf()).

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/cpu/spl.c b/arch/sandbox/cpu/spl.c
index 1ad7fb6..632446b 100644
--- a/arch/sandbox/cpu/spl.c
+++ b/arch/sandbox/cpu/spl.c
@@ -51,7 +51,7 @@
 	/* Hopefully this will not return */
 	return os_spl_to_uboot(fname);
 }
-SPL_LOAD_IMAGE_METHOD(0, BOOT_DEVICE_BOARD, spl_board_load_image);
+SPL_LOAD_IMAGE_METHOD("sandbox", 0, BOOT_DEVICE_BOARD, spl_board_load_image);
 
 void spl_board_init(void)
 {