drm/i915/glk: Implement Geminilake DDI init sequence

Implement the DDI initsequence and add information about the different
phys in GLK.

v2: Rebase on the move of phys to be power wells.

v3: Rebase on addition of struct bxt_ddi_phy_info.

Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480667037-11215-4-git-send-email-ander.conselvan.de.oliveira@intel.com