dummyflasher: Replace another case of `sizeof(struct ...)`

Using the pointer's type instead ensures that we get the right size even
if code changes in the future.

Change-Id: If88ba394095f86c598dcc5cf1751e1c23b132d04
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/55358
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 b75cddb..6a75506 100644
--- a/dummyflasher.c
+++ b/dummyflasher.c
@@ -947,7 +947,7 @@
 {
 	struct stat image_stat;
 
-	struct emu_data *data = calloc(1, sizeof(struct emu_data));
+	struct emu_data *data = calloc(1, sizeof(*data));
 	if (!data) {
 		msg_perr("Out of memory!\n");
 		return 1;