MAINTAINERS: Replace Claudio Fontana for tcg/aarch64

MAINTAINERS: Replace Claudio Fontana for tcg/aarch64

Claudio's Huawei address has been defunct for quite a while.  In

  https://lists.gnu.org/archive/html/qemu-devel/2019-05/msg06872.html

he asked for his personal address to be removed as well.

I will take over officially.

Cc: Claudio Fontana <claudio.fontana@gmail.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>