staging: rtl8723au: Use ARRAY_SIZE macro for sizes of arrays

Use ARRAY_SIZE to calculate the size of an array to make code concise.
The semantic patch used can be found here:
https://github.com/coccinelle/coccinellery/commit/9cbab452a3a2e18439e8386d6c4a68ee42c3ee2b



Signed-off-by: Janani Ravichandran <janani.rvchndrn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>