target/riscv: rvv: Provide a fast path using direct access to host ram for unit-strid...

target/riscv: rvv: Provide a fast path using direct access to host ram for unit-stride whole register load/store

The vector unit-stride whole register load/store instructions are
similar to unmasked unit-stride load/store instructions that is suitable
to be optimized by using a direct access to host ram fast path.

Because the vector whole register load/store instructions do not need to
handle the tail agnostic, so remove the vstart early exit checking.

Signed-off-by: Max Chou <max.chou@sifive.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20240918171412.150107-5-max.chou@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>