MAINTAINERS: switch to my private email for Renesas Ethernet drivers

I no longer work for Cogent Embedded (but my old email still works :-)),
and still would like to continue looking after the Renesas Ethernet drivers
and bindings.  Let's switch to my private email.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -14538,7 +14538,7 @@ F:	Documentation/devicetree/bindings/i2c/renesas,iic-emev2.txt
 F:	drivers/i2c/busses/i2c-emev2.c
 
 RENESAS ETHERNET DRIVERS
-R:	Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
+R:	Sergei Shtylyov <sergei.shtylyov@gmail.com>
 L:	netdev@vger.kernel.org
 L:	linux-renesas-soc@vger.kernel.org
 F:	Documentation/devicetree/bindings/net/renesas,*.txt