Using struct drm_device.pdev is deprecated. Convert amdgpu to struct
drm_device.dev. No functional changes.

v3:
	* rebased
Signed-off-by: NThomas Zimmermann <tzimmermann@suse.de>
Acked-by: NChristian König <christian.koenig@amd.com>
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Acked-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210107080748.4768-3-tzimmermann@suse.de