MAINTAINERS: eth: mvneta: move Thomas to CREDITS

Thomas is still active in other bits of the kernel and beyond
but not as much on the Marvell Ethernet devices.
Our scripts report:

Subsystem MARVELL MVNETA ETHERNET DRIVER
  Changes 54 / 176 (30%)
  (No activity)
  Top reviewers:
    [12]: hawk@kernel.org
    [9]: toke@redhat.com
    [9]: john.fastabend@gmail.com
  INACTIVE MAINTAINER Thomas Petazzoni <thomas.petazzoni@bootlin.com>

Acked-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Link: https://lore.kernel.org/r/20240109164517.3063131-4-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>