drm/i915/icl: remove port A/E lane sharing limitation.

Platforms before Gen11 were sharing lanes between port-A & port-E.
This limitation is no more there.

Changes since V1:
 - optimize the code (Shashank/Jani)
 - create helper function to get max lanes (ville)
Changes since V2:
 - Include BIOS fail fix-up in same helper function (ville)
Changes since V3:
 - remove confusing if/else (jani)
 - group intel_encoder initialization

Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180206060855.30026-1-mahesh1.kumar@intel.com