drm/i915: update FDI mPHY setup code

Bspec has been been updated and dropped these two changes for non-sdv
LPT PCHs.

Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>