target/riscv: rvv-1.0: Call the correct RVF/RVD check function for narrowing fp/int...

target/riscv: rvv-1.0: Call the correct RVF/RVD check function for narrowing fp/int type-convert insns

vfncvt.f.xu.w, vfncvt.f.x.w convert double-width integer to single-width
floating-point. Therefore, should use require_rvf() to check whether
RVF/RVD is enabled.

vfncvt.f.f.w, vfncvt.rod.f.f.w convert double-width floating-point to
single-width integer. Therefore, should use require_scale_rvf() to check
whether RVF/RVD is enabled.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20220105022247.21131-4-frank.chang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>