dwc-xlgmac: remove Jie Deng as co-maintainer

Jose Abreu is working on this driver and I will leave Synopsys soon.
Thus it does not seem appropriate for me to be a co-maintainer anymore.

Signed-off-by: Jie Deng <jiedeng@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>