drm/i915/tv: Fix tv mode clocks

The oversample clock is always supposed to be either 108 MHz
or 148.5 MHz. Make it so.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181112170000.27531-5-ville.syrjala@linux.intel.com


Reviewed-by: Imre Deak <imre.deak@intel.com>