media: ccs-pll: Fix condition for pre-PLL divider lower bound

The lower bound of the pre-PLL divider was calculated based on OP SYS
clock frequency which is also affected by the OP SYS clock divider. This
is wrong. The right clock frequency is that of the PLL output clock.

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