spl: Add a parameter to spl_parse_image_header()

Instead of using the global spl_image variable, pass the required struct in
as an argument.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/common/spl/spl_net.c b/common/spl/spl_net.c
index ae71d26..f417d17 100644
--- a/common/spl/spl_net.c
+++ b/common/spl/spl_net.c
@@ -34,5 +34,6 @@
 		printf("Problem booting with BOOTP\n");
 		return rv;
 	}
-	return spl_parse_image_header((struct image_header *)load_addr);
+	return spl_parse_image_header(&spl_image,
+				      (struct image_header *)load_addr);
 }