target/arm/kvm: Merge kvm64.c into kvm.c

target/arm/kvm: Merge kvm64.c into kvm.c

Since kvm32.c was removed, there is no need to keep them separate.
This will allow more symbols to be unexported.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
[PMM: retain copyright lines from kvm64.c in kvm.c]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>