MAINTAINERS: Drop myself as xen netback maintainer

Wei has been picking this up for quite a while now.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -12021,7 +12021,6 @@ F:	arch/arm64/xen/
 F:	arch/arm64/include/asm/xen/
 
 XEN NETWORK BACKEND DRIVER
-M:	Ian Campbell <ian.campbell@citrix.com>
 M:	Wei Liu <wei.liu2@citrix.com>
 L:	xen-devel@lists.xenproject.org (moderated for non-subscribers)
 L:	netdev@vger.kernel.org