Exynos: clock: change mask bits as per peripheral

We have assumed and kept mask bits for divider and pre-divider
as 0xf and 0xff, respectively. But these mask bits change from
one peripheral to another, and hence, need to be specified in
accordance with the peripherals.

Signed-off-by: Akshay Saraswat <akshay.s@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>