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 <[email protected]>
Signed-off-by: Yipeng Yin <[email protected]>
Signed-off-by: Alistair Francis <[email protected]>
Reviewed-by: Alistair Francis <[email protected]>
Message-id: 20201026115530[email protected]