treewide: Drop most cases of `sizeof(struct ...)`

Spelling out the struct type name hurts readability and introduces
opportunities for bugs to happen when the pointer variable type is
changed but the corresponding sizeof is (are) not.

Tested: `make CONFIG_EVERYTHING=yes CONFIG_JLINK_SPI=no VERSION=none -j`
with and without this patch; the flashrom executable does not change.

flashrom-stable: Applied partially.

Change-Id: Icc0b60ca6ef9f5ece6ed2a0e03600bb6ccd7dcc6
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/55266
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Original-Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/71371
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/hwaccess.c b/hwaccess.c
index 48ccb34..3a9ca57 100644
--- a/hwaccess.c
+++ b/hwaccess.c
@@ -247,7 +247,7 @@
 #define register_undo_mmio_write(a, c)					\
 {									\
 	struct undo_mmio_write_data *undo_mmio_write_data;		\
-	undo_mmio_write_data = malloc(sizeof(struct undo_mmio_write_data)); \
+	undo_mmio_write_data = malloc(sizeof(*undo_mmio_write_data));	\
 	if (!undo_mmio_write_data) {					\
 		msg_gerr("Out of memory!\n");				\
 		exit(1);						\