drm/xe/mtl: Use 16.67 Mhz freq scale factor to get rpX

For mtl and above 16.67 Mhz is the scale factor to calculate
rpX frequencies.

v2: Fix review comment (Ashutosh)

Signed-off-by: Badal Nilawar <badal.nilawar@intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231101163212.1629685-1-badal.nilawar@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>