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 load-only-first load instructions

The unmasked unit-stride fault-only-first load instructions are similar
to the unmasked unit-stride load/store instructions that is suitable to
be optimized by using a direct access to host ram fast path.

Signed-off-by: Max Chou <max.chou@sifive.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20240918171412.150107-6-max.chou@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>