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: John Keeping <john@metanate.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/common/spl/spl.c b/common/spl/spl.c
index 3b96f2f..3ec16d0 100644
--- a/common/spl/spl.c
+++ b/common/spl/spl.c
@@ -200,7 +200,7 @@
 	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 @@
 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)