MAINTAINERS: step down as TJA11XX C45 maintainer

I am stepping down as TJA11XX C45 maintainer.
Andrei Botila will take the responsibility to maintain and improve the
support for TJA11XX C45 PHYs.

Signed-off-by: Radu Pirea (NXP OSS) <radu-nicolae.pirea@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>