staging: rtl8723au: hal: Use macro ARRAY_SIZE

The macro ARRAY_SIZE is more concise to use instead of dividing
size of the array by the size of its type.

Changes were made using Coccinelle.

@@
type T;
T[] E;
@@

- (sizeof(E)/sizeof(T))
+ ARRAY_SIZE(E)

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>