PCI: designware: Change maintainer to Joao Pinto

I accepted the invitation from Pratyush to replace him in the
pcie-designware maintenance.  This patch makes the maintainer replacement
and simplifies the pcie-designware* maintenance structure.

Signed-off-by: Joao Pinto <jpinto@synopsys.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Pratyush Anand <pratyush.anand@gmail.com>
CC: Jose Abreu <Jose.Abreu@synopsys.com>