dummyflasher.c: Fix use-after-free issue

Issue accidentally introduced in commit e3707bbf4.

BUG=none
BRANCH=none
TEST=builds

Change-Id: Ie12d6474ef5a7bb1afbbb9ec50b31b577da1a81b
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/55014
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>
diff --git a/dummyflasher.c b/dummyflasher.c
index b7cfab8..325263d 100644
--- a/dummyflasher.c
+++ b/dummyflasher.c
@@ -700,12 +700,13 @@
 	tmp = extract_programmer_param("spi_write_256_chunksize");
 	if (tmp) {
 		data->spi_write_256_chunksize = strtoul(tmp, &endptr, 0);
-		free(tmp);
 		if (*endptr != '\0' || data->spi_write_256_chunksize < 1) {
 			msg_perr("invalid spi_write_256_chunksize\n");
+			free(tmp);
 			return 1;
 		}
 	}
+	free(tmp);
 
 	tmp = extract_programmer_param("spi_blacklist");
 	if (tmp) {