drm/i915/ICL: Add pre_pll_enable hook for ICL and set DFLEXDPMLE in this hook

In case of Legacy DP connector on TypeC port, the
flex IO DPMLE register is set to number of lanes configured
by the display driver which will be programmed into DDI_BUF_CTL
PORT_WIDTH_SELECTION.
This needs to be programmed before enabling the shared PLLs hence
add a pre_pll_enable hook for ICL and add this programming in that hook.

v2:
* Remove the check for combophy port (Jose)
* Simplify the port reversal check logic (Jose)

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Jose Roberto de Souza <jose.souza@intel.com>
Cc: Animesh Manna <animesh.manna@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Acked-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181023191248.26418-2-manasi.d.navare@intel.com