i2c-piix4: Add Hygon Dhyana SMBus support

The Hygon Dhyana CPU has the SMBus device with PCI device ID 0x790b,
which is the same as AMD CZ SMBus device. So add Hygon Dhyana support
to the i2c-piix4 driver by using the code path of AMD.

Signed-off-by: Pu Wen <puwen@hygon.cn>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>