media: ccs-pll: Fix check for PLL multiplier upper bound

The additional multiplier (for higher VT timing) of the PLL multiplier was
checked against the upper limit but the result was rounded up, possibly
producing too high additional multiplier. Round down instead to keep
within hardware limits.

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