target/riscv/insn_trans/trans_rvv.c.inc: use 'vlenb' in MAXSZ()

target/riscv/insn_trans/trans_rvv.c.inc: use 'vlenb' in MAXSZ()

Calculate the maximum vector size possible, 'max_sz', which is the size
in bytes 'vlenb' multiplied by the max value of LMUL (LMUL = 8, when
s->lmul = 3).

'max_sz' is then shifted right by 'scale', expressed as '3 - s->lmul',
which is clearer than doing 'scale = lmul - 3' and then using '-scale'
in the shift right.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240122161107.26737-10-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>