hisi_sas: Remove dependency on of_irq_count

Originally the driver would use of_irq_count to calculate how much
memory is required for storing the interrupt names, since the number of
interrupt sources for the controller is variable.  Since of_irq_count
cannot be used by the driver, use fixed names.

Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>