target/riscv: Merge m/vsstatus and m/vsstatush into one uint64_t unit

target/riscv: Merge m/vsstatus and m/vsstatush into one uint64_t unit

mstatus/mstatush and vsstatus/vsstatush are two halved for RISCV32.
This patch expands mstatus and vsstatus to uint64_t instead of
target_ulong so that it can be saved as one unit and reduce some
ifdefs in the code.

Signed-off-by: Yifei Jiang <jiangyifei@huawei.com>
Signed-off-by: Yipeng Yin <yinyipeng1@huawei.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20201026115530.304-2-jiangyifei@huawei.com