lib/stackdepot.c: use array_size() helper in jhash2()

Use array_size() helper instead of the open-coded version in jhash2().
These sorts of multiplication factors need to be wrapped in array_size().

Also, use the preferred form for passing the size of an object type.

Link: https://lkml.kernel.org/r/cb8a682e4bba4dbddd2bd8aca7f8c02fea89639b.1601565471.git.gustavoars@kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/stackdepot.c

@@ -154,8 +154,8 @@ static struct stack_record *stack_table[STACK_HASH_SIZE] = {
 static inline u32 hash_stack(unsigned long *entries, unsigned int size)
 {
 	return jhash2((u32 *)entries,
-			       size * sizeof(unsigned long) / sizeof(u32),
-			       STACK_HASH_SEED);
+		      array_size(size,  sizeof(*entries)) / sizeof(u32),
+		      STACK_HASH_SEED);
 }
 
 /* Use our own, non-instrumented version of memcmp().