hw/loongarch: Rename LoongArchMachineState with LoongArchVirtMachineState

hw/loongarch: Rename LoongArchMachineState with LoongArchVirtMachineState

Rename LoongArchMachineState with LoongArchVirtMachineState, and change
variable name LoongArchMachineState *lams with LoongArchVirtMachineState
*lvms.

Rename function specific for virtmachine loongarch_xxx()
with virt_xxx(). However some common functions keep unchanged such as
loongarch_acpi_setup()/loongarch_load_kernel(), since there functions
can be used for real hw boards.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240508031110.2507477-3-maobibo@loongson.cn>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>