target/riscv: Pass the same value to oprsz and maxsz for vmv.v.v

oprsz and maxsz are passed with the same value in commit: eee2d61e.
However, vmv.v.v was missed in that commit and should pass the same
value as well in its tcg_gen_gvec_2_ptr() call.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20211007081803.1705656-1-frank.chang@sifive.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>