target/riscv: rvv-1.0: Add Zve64f support for load and store insns

target/riscv: rvv-1.0: Add Zve64f support for load and store insns

All Zve* extensions support all vector load and store instructions,
except Zve64* extensions do not support EEW=64 for index values when
XLEN=32.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20220118014522.13613-4-frank.chang@sifive.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>