MAINTAINERS: Update my email address

MAINTAINERS: Update my email address

I am leaving Xilinx, so to avoid having an email address that bounces
update my maintainer address to point to my personal email address.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Signed-off-by: Alistair Francis <alistair@alistair23.me>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 7bb690382e3370aa1c1e047a84e36603c787ec0e.1519749987.git.alistair.francis@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>