set: check seek success

This could silently fail which leads to surprising behaviour.

Found-by: Coverity Scan
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>

src/set.c

diff --git a/src/set.c b/src/set.c
index ff32b53..0af6686 100644
--- a/src/set.c
+++ b/src/set.c
@@ -59,7 +59,11 @@
 		return result;
 	}
 
-	fseek(fp, offset, SEEK_SET);
+	if (fseek(fp, offset, SEEK_SET) == -1) {
+		printf("Error: Couldn't seek to %s(%d)\n", filename, offset);
+		result = 1;
+		goto cleanup;
+	}
 
 	if (stat(filename, &stats) != 0) {
 		printf("Error: Unable to query info on bootloader path %s\n",