drm/i915/display: Pass drm_i915_private as param to i915 funcs

For i915 functions pass struct drm_i915_private directly instead of
struct drm_device.

v2: Use to_i915(dev) directly without alias(Andrzej).

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Suggested-by: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230125095603.17845-1-nirmoy.das@intel.com