util/nvmutil: reset errno before run_cmd

in case any stale errors are present.

at this point, we know that the code is likely
safe and that nothing happened, because we quite
obsessively call err() before that point.

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/nvmutil/nvmutil.c

@@ -505,6 +505,7 @@ main(int argc, char *argv[])
 	read_gbe_file();
 	read_checksums();
 
+	errno = 0;
 	run_cmd(cmd_index);
 
 	if (errno)