drm/i2c: tda998x: move tda998x_set_config() into tda998x_create()

Move the non-DT configuration of the TDA998x into tda998x_create()
so that we do all setup in one place.

Tested-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>