drm/i915/bios: mass convert dev_priv to i915

Time to just yank out the bandage. No functional changes.

v2: Rebased

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> # v1
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/93fe9e8be2e6120b085d09e49aafdf52f5ccd725.1615998927.git.jani.nikula@intel.com