target/loongarch: Add TCG macro in structure CPUArchState

target/loongarch: Add TCG macro in structure CPUArchState

In structure CPUArchState some struct elements are only used in TCG
mode, and it is not used in KVM mode. Macro CONFIG_TCG is added to
make it simpiler in KVM mode, also there is the same modification
in c code when these structure elements are used.

When VM runs in KVM mode, TLB entries are not used and do not need
migrate. It is only useful when it runs in TCG mode.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20240506011912.2108842-1-maobibo@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>