staging: rtl8723bs: use DIV_ROUND_UP helper macro

Use the DIV_ROUND_UP macro to replace open-coded divisor calculation
to improve readability.
Issue found using coccinelle:
@@
expression n,d;
@@
(
- ((n + d - 1) / d)
+ DIV_ROUND_UP(n,d)
|
- ((n + (d - 1)) / d)
+ DIV_ROUND_UP(n,d)
)

Signed-off-by: Wambui Karuga <wambui.karugax@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Link: https://lore.kernel.org/r/20191013191027.6470-1-wambui.karugax@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>