target/riscv: Fix implementation of HLVX.WU instruction

target/riscv: Fix implementation of HLVX.WU instruction

The HLVX.WU instruction is supposed to read a machine word,
but prior to this change it read a byte instead.

Fixes: 8c5362acb57 ("target/riscv: Allow generating hlv/hlvx/hsv instructions")
Signed-off-by: Georg Kotheimer <georg.kotheimer@kernkonzept.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20201013172223.443645-1-georg.kotheimer@kernkonzept.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>