i2c: hix5hd2: allow build with ARCH_HISI

This driver should be buildable with ARCH_HISI,
because some of other HiSilicon SoCs also use it.

Signed-off-by: Ruqiang Ju <juruqiang@huawei.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>