MAINTAINERS: Orphan Cadence PCIe IP

Tom Joseph <tjoseph@cadence.com> is listed as the maintainer of the Cadence
PCIe IP, but email to that address bounces and lore has no correspondence
from Tom in the past two years
(https://lore.kernel.org/all/?q=f%3Atjoseph).

Mark the Cadence IP orphaned and add Tom to CREDITS.

Link: https://lore.kernel.org/r/20240102182157.GA1732664@bhelgaas


Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>