IB/hns: Change the logic for allocating uar registers

This patch mainly modifies the logic for allocating uar registers.
In HiP06 SoC, HW has 8 group of uar registers for kernel and
user space application. The uar index is assigned as follows:
    0   ------ for kernel
    1~7 ------ for user space application

Signed-off-by: Lijun Ou <oulijun@huawei.com>
Reviewed-by: Wei Hu <xavier.huwei@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>