Before hardware V3, hardwares do not provide the feature registers,
driver resolves hardware differences based on the hardware version.
As a result, the driver does not support the new hardware.

Hardware V3 and later versions support to obtain hardware features,
such as power-gating management and doorbell isolation, through
the hardware registers. To be compatible with later hardware versions,
the features of the current device is obtained by reading the
hardware registers instead of the hardware version.
Signed-off-by: Weili Qian <qianweili@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>