MAINTAINERS: Update email-id of Rahul Bedarkar

I'm no longer with Imagination Technologies. I am still interested in
maintaining or reviewing DTS patches for Ci40 if any. Update email-id
to an active one.

Signed-off-by: Rahul Bedarkar <rahulbedarkar89@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/15990/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>