kvm/mips: update MAINTAINERS

Aleksandar Markovic was last seen in Oct 2020 [1] and cannot be
reached for multiple days because of "Recipient inbox full".

[1] https://lore.kernel.org/all/1602103041-32017-4-git-send-email-aleksandar.qemu.devel@gmail.com/



Signed-off-by: Yu Zhao <yuzhao@google.com>
Acked-by: Huacai Chen <chenhuacai@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>