Fix the return value check which testing the wrong variable
in mt7621_pci_phy_probe().

Fixes: d87da323 ("phy: ralink: Add PHY driver for MT7621 PCIe PHY")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20210305034931.3237558-1-weiyongjun1@huawei.comSigned-off-by: Vinod Koul <vkoul@kernel.org>