spl: Create a function to init spl_load_info

Rather than having every caller set this up individually, create a
common init function. This allows new fields to be added without the
risk of them being left uninited.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Michael Trimarchi <michael@amarulasolutions.com>
diff --git a/test/image/spl_load_os.c b/test/image/spl_load_os.c
index 56105a5..d17cf11 100644
--- a/test/image/spl_load_os.c
+++ b/test/image/spl_load_os.c
@@ -20,3 +20,4 @@
 	return 0;
 }
 SPL_TEST(spl_test_load, 0);
+