drm/i915: Write AVI infoframes for MCA LSPCON

drm/i915: Write AVI infoframes for MCA LSPCON

LSPCON is a DP branch device, so LSPCON vendors define
specific methods to pass AVI infoframes to the the chip.
This patch adds:
- a generic wrapper function for writing AVI infoframes for
  all LSPCON devices.
- a vendor specific function to wrire AVI infoframes into
  MCA LSPCON devices.

V2: Rebase
V3: Added r-b from Maarten
V4: Rebase
V5: Rebase
V6: Rebase
V7: Fixed checkpatch warnings for alignment
V8: Rebase
V9: Added the retry logic, with 50ms incremental delays while
    writing AVI IF
V10: Changed the return value check
V11: Fixed checkpatch warning
V12: Rebase

Cc: Imre Deak <imre.deak@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1539325394-20788-6-git-send-email-shashank.sharma@intel.com