spl: use CONFIG_IS_ENABLED(LOAD_FIT_FULL)

It's possible that LOAD_FIT_FULL will have different values for TPL and
SPL, in which case just checking CONFIG_SPL_LOAD_FIT_FULL causes this to
be compiled in to the TPL even though functions and struct members it
depends on are not.

Use CONFIG_IS_ENABLED() to ensure the correct TPL/SPL variant is
checked.
Signed-off-by: NJohn Keeping <john@metanate.com>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>
Reviewed-by: NSimon Glass <sjg@chromium.org>

common/spl/spl.c

@@ -200,7 +200,7 @@ void spl_set_header_raw_uboot(struct spl_image_info *spl_image)
 	spl_image->name = "U-Boot";
 }
 
-#ifdef CONFIG_SPL_LOAD_FIT_FULL
+#if CONFIG_IS_ENABLED(LOAD_FIT_FULL)
 /* Parse and load full fitImage in SPL */
 static int spl_load_fit_image(struct spl_image_info *spl_image,
 			      const struct image_header *header)
@@ -307,7 +307,7 @@ __weak int spl_parse_legacy_header(struct spl_image_info *spl_image,
 int spl_parse_image_header(struct spl_image_info *spl_image,
 			   const struct image_header *header)
 {
-#ifdef CONFIG_SPL_LOAD_FIT_FULL
+#if CONFIG_IS_ENABLED(LOAD_FIT_FULL)
 	int ret = spl_load_fit_image(spl_image, header);
 
 	if (!ret)