drm/i915: Remove reference to struct drm_device.pdev

References to struct drm_device.pdev should not be used any longer as
the field will be moved into the struct's legacy section. Fix a rsp
comment.

v8:
	* fix commit message (Michael)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210429105101.25667-4-tzimmermann@suse.de