MAINTAINERS: Add Manivannan Sadhasivam as Reviewer for PCI native host bridge and endpoint drivers

I've been reviewing the native host bridge drivers for some time and would
like to be listed as a Reviewer formally.

Link: https://lore.kernel.org/r/20240812055707.6778-1-manivannan.sadhasivam@linaro.org


Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>