staging: r8188eu: use round_up() instead of _RND8()

Use in-kernel round_up() instead of custom _RND8().
Just remove _RND8 where it is not necessary to round up.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220407125742.7814-4-straube.linux@gmail.com


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