qtnfmac: fix error return code in qtnf_pcie_probe()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: b7da53cd ("qtnfmac_pcie: use single PCIe driver for all platforms")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201114123347.29632-1-wanghai38@huawei.com