MAINTAINERS: co-maintainance of KVM/{arm,arm64}

MAINTAINERS: co-maintainance of KVM/{arm,arm64}

The KVM/{arm,arm64} ports are sharing a lot of code, and are
effectively co-maintained (and have been for quite a while).

Make the situation official and list the two maintainers
for both ports.

Cc: Catalin Marinas <[email protected]>
Cc: Russell King <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Gleb Natapov <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Signed-off-by: Christoffer Dall <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>