crypto: hisilicon/sec - enabling clock gating of the address prefetch module

Change the value of clock gating register to 0x7fff to enable
clock gating of the address prefetch module. When the device is
idle, the clock is turned off to save power.

Signed-off-by: Weili Qian <qianweili@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>