Add subsystem callbacks for VT8237x and VT890 family of chipsets

Add subsystem callbacks for VT8237x and VT890 family of chipsets

Change-Id: Id34615f0c229d276d72cdf984cf82ea8cc1a85bb
Signed-off-by: Rudolf Marek <r.marek@assembler.cz>
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/523
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>