firmware-utils: uimage_padhdr: fix Coverity issue
Fixes following issue reported by Coverity scan:
*** CID
1452085: Security best practices violations (TOCTOU)
/tools/firmware-utils/src/uimage_padhdr.c: 100 in main()
94
95 if (!infname || !outfname) {
96 usage(argv[0]);
97 exit(1);
98 }
99
>>> CID
1452085: Security best practices violations (TOCTOU)
>>> Calling function "stat" to perform check on "infname".
100 if (stat(infname, &statbuf) < 0) {
Fixes: a1c6a316d299 ("ramips: add support for Fon FON2601")
Signed-off-by: Petr Štetiar <ynezz@true.cz>