drm/radeon: convert to use i2c_new_client_device()

Move away from the deprecated API.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200326211005.13301-7-wsa+renesas@sang-engineering.com