media: ccs-pll: Make VT divisors 16-bit

Make VT divisors 16-bit unsigned numbers. They don't need 32 bits after
all.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>