nvdimm/btt: use sizeof(*pointer) instead of sizeof(type)

It is preferred to use sizeof(*pointer) instead of sizeof(type)
due to the type of the variable can change and one needs not
change the former (unlike the latter). This patch has no effect
on runtime behavior.

Signed-off-by: Erick Archer <erick.archer@outlook.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/r/AS8PR02MB72372490C53FB2E35DA1ADD08BFE2@AS8PR02MB7237.eurprd02.prod.outlook.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>

Author: Erick Archer

drivers/nvdimm/btt.c

@@ -751,7 +751,7 @@ static struct arena_info *alloc_arena(struct btt *btt, size_t size,
 	u64 logsize, mapsize, datasize;
 	u64 available = size;
 
-	arena = kzalloc(sizeof(struct arena_info), GFP_KERNEL);
+	arena = kzalloc(sizeof(*arena), GFP_KERNEL);
 	if (!arena)
 		return NULL;
 	arena->nd_btt = btt->nd_btt;
@@ -978,7 +978,7 @@ static int btt_arena_write_layout(struct arena_info *arena)
 	if (ret)
 		return ret;
 
-	super = kzalloc(sizeof(struct btt_sb), GFP_NOIO);
+	super = kzalloc(sizeof(*super), GFP_NOIO);
 	if (!super)
 		return -ENOMEM;