mhi: pci_generic: Add PCI error handlers

In AER capable root complex, errors are reported to the host which
can then act accordingly and perform PCI recovering procedure.

This patch enables error reporting and implements error_detected,
slot_reset and resume callbacks.

Reviewed-by Hemant Kumar <hemantk@codeaurora.org>

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>