drm/i915/dp: Remove -1/+1 from t11_t12 for Gen9_LP/CNP case

drm/i915/dp: Remove -1/+1 from t11_t12 for Gen9_LP/CNP case

Now the VBT.seq->t11_t12 value adds 100ms to both Gen9_LP
as well as non Gen9_LP cases so no need to special case
and do -1 during HW readout and +1 during pp_div write
for Gen9_LP/CNP case.

Reviewed-by: Ville Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Suggested-by: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Clint Taylor <clinton.a.taylor@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1498504905-21067-2-git-send-email-manasi.d.navare@intel.com
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>