bus: mhi: pci_generic: Add mru_default for Cinterion MV31-W

bus: mhi: pci_generic: Add mru_default for Cinterion MV31-W

For default mechanism, product would use default MRU 3500 if
they didn't define it. But for Cinterion MV31-W, 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 # v5.14 +
Fixes: 87693e092bd0 ("bus: mhi: pci_generic: Add Cinterion MV31-W PCIe to MHI")
Signed-off-by: Slark Xiao <slark_xiao@163.com>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://lore.kernel.org/r/20220119102519.5342-1-slark_xiao@163.com
[mani: Modified the commit message to reflect Cinterion MV31-W and CCed stable]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>