drm/i915/fdi: move fdi mphy reset and programming to intel_fdi.c

This fairly detailed stuff that really has no place in
intel_display.c. Combine the calls into one to avoid exposing both.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b0037775480380e5d73d0b112da478d6f0ea30fe.1629906431.git.jani.nikula@intel.com