mmc: core: Calculate size from pointer

Calculate the size from pointer instead of
struct to adhere to linux kernel coding style.

Issue reported by checkpatch.

This commit has no functional changes.

Signed-off-by: Riyan Dhiman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Ulf Hansson <[e-mail]>

drivers/mmc/core/block.c

···
 		return ERR_PTR(devidx);
 	}
 
-	md = kzalloc(sizeof(struct mmc_blk_data), GFP_KERNEL);
+	md = kzalloc(sizeof(*md), GFP_KERNEL);
 	if (!md) {
 		ret = -ENOMEM;
 		goto out;