drm/i915/glk: Program dphy param reg for GLK

For GEMINILAKE, dphy param reg values are programmed in terms
of HS byte clock count while for older platforms in terms of
HS ddr clk count.

v2: Added comments to clarify ddr clock count calculation
v3: Use multiplier variable instead of IS_GEMINILAKE()
check everywhere (Jani)

Signed-off-by: Deepak M <m.deepak@intel.com>
Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1487335415-14766-2-git-send-email-madhav.chauhan@intel.com