MAINTAINERS: Add Manivannan Sadhasivam as PCI Endpoint reviewer

I've been reviewing the patches related to PCI Endpoint Subsystem for some
time. So I'd like to add myself as the reviewer to get immediate attention
to the patches.

Link: https://lore.kernel.org/r/20220819020817.197844-1-manivannan.sadhasivam@linaro.org


Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>