media: ccs-pll: Don't use div_u64 to divide a 32-bit number

pll->pll_op_clk_freq is a 32-bit number. It does not need div_u64 to
divide it.

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