spl: Improve error message for SPL memory allocation

There could be two memory allocation scheme in SPL phase.
Explicitly print the corresponding error message.

Signed-off-by: Leo Yu-Chi Liang <ycliang@andestech.com>
diff --git a/common/spl/spl_fit.c b/common/spl/spl_fit.c
index 872df0c..e5195d4 100644
--- a/common/spl/spl_fit.c
+++ b/common/spl/spl_fit.c
@@ -550,7 +550,12 @@
 	buf = malloc_cache_aligned(size);
 	if (!buf) {
 		pr_err("Could not get FIT buffer of %lu bytes\n", (ulong)size);
-		pr_err("\tcheck CONFIG_SPL_SYS_MALLOC_SIZE\n");
+
+		if (IS_ENABLED(CONFIG_SPL_SYS_MALLOC))
+			pr_err("\tcheck CONFIG_SPL_SYS_MALLOC_SIZE\n");
+		else
+			pr_err("\tcheck CONFIG_SPL_SYS_MALLOC_F_LEN\n");
+
 		buf = spl_get_load_buffer(0, size);
 	}
 	return buf;