staging: rtl8723au: hal: Use macro DIV_ROUND_UP

The macro DIV_ROUND_UP performs the computation
(((n) + (d) - 1) /(d)). It clarifies the divisor calculations.
This was done using the coccinelle script:
@@
expression e1;
expression e2;
@@
(
- ((e1) + e2 - 1) / (e2)
+ DIV_ROUND_UP(e1,e2)
|
- ((e1) + (e2 - 1)) / (e2)
+ DIV_ROUND_UP(e1,e2)
)

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