According to the tool fortify, phy_up_v3_hw() returns signed value, while
it should return an unsigned value.

So change variable "res" from int to irq_return_t.
Signed-off-by: NXiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: NJohn Garry <john.garry@huawei.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>