drm/i915/huc: Add BXT HuC Loading Support

This patch adds the HuC Loading for the BXT by using
the updated file construction.

Version 1.7 of the HuC firmware.

v2: rebased on to top drm-tip. Rename BXT_FW_MAJOR to BXT_HUC_FW_

Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1484755558-1234-2-git-send-email-anusha.srivatsa@intel.com