drm/i915/uc: Make GuC/HuC fw fetch and loading functions/file structure symmetric

drm/i915/uc: Make GuC/HuC fw fetch and loading functions/file structure symmetric

GuC load function is named intel_guc_fw_upload() and HuC load function is
named intel_huc_init_hw(). Make them consistent intel_*_fw_upload. Also
move HuC fw loading functions and declarations to separate files
intel_huc_fw.c|h like GuC.

While at this, do below changes
1. Update kernel-doc comment for intel_*_fw_upload() functions
2. s/huc_ucode_xfer/huc_fw_xfer
3. Introduce intel_huc_fw_init_early()

v2: Changed patch to update HuC functions instead of changing
    guc_fw_upload and update file structure. (Michal Wajdeczko)

v3: Added SPDX License identifier to huc_fw.c|h. (Michal Wajdeczko)

Signed-off-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/1519922745-25441-1-git-send-email-sagar.a.kamble@intel.com