bus: mhi: pci_generic: Add mru_default for Foxconn SDX55

bus: mhi: pci_generic: Add mru_default for Foxconn SDX55

For default mechanism, product would use default MRU 3500 if
they didn't define it. But for Foxconn SDX55, there is a known
issue which MRU 3500 would lead to data connection lost.
So we align it with Qualcomm default MRU settings.

Cc: stable@vger.kernel.org # v5.12+
Fixes: aac426562f56 ("bus: mhi: pci_generic: Introduce Foxconn T99W175 support")
Signed-off-by: Slark Xiao <slark_xiao@163.com>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://lore.kernel.org/r/20220119101213.5008-1-slark_xiao@163.com
[mani: Added pci_generic prefix to subject and CCed stable]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>