mmc: sdhci-pci-o2micro: Add missing checks in sdhci_pci_o2_probe

It's odd to adopt different error handling on failure of
pci_read_config_dword(). Check the return value and terminate
execution flow on failure of all pci_read_config_dword() calls
in this function.

Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
Link: https://lore.kernel.org/r/20210226084146.29095-1-dinghao.liu@zju.edu.cn
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>