tools: relocate-rela: Open binary u-boot file later

There is no value to open u-boot binary file so early. Better to check all
values first and then open binary file.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/9c2b4ebadbe83497db28af02f6af2623793ffdb6.1655299267.git.michal.simek@amd.com
diff --git a/tools/relocate-rela.c b/tools/relocate-rela.c
index f0bc548..8839871 100644
--- a/tools/relocate-rela.c
+++ b/tools/relocate-rela.c
@@ -73,13 +73,6 @@
 		return 1;
 	}
 
-	f = fopen(argv[1], "r+b");
-	if (!f) {
-		fprintf(stderr, "%s: Cannot open %s: %s\n",
-			argv[0], argv[1], strerror(errno));
-		return 2;
-	}
-
 	if (!read_num(argv[2], &text_base) ||
 	    !read_num(argv[3], &rela_start) ||
 	    !read_num(argv[4], &rela_end)) {
@@ -95,6 +88,13 @@
 	rela_start -= text_base;
 	rela_end -= text_base;
 
+	f = fopen(argv[1], "r+b");
+	if (!f) {
+		fprintf(stderr, "%s: Cannot open %s: %s\n",
+			argv[0], argv[1], strerror(errno));
+		return 2;
+	}
+
 	fseek(f, 0, SEEK_END);
 	file_size = ftell(f);
 	rewind(f);