target/i386/tcg: fix POP to memory in long mode

target/i386/tcg: fix POP to memory in long mode

In long mode, POP to memory will write a full 64-bit value.  However,
the call to gen_writeback() in gen_POP will use MO_32 because the
decoding table is incorrect.

The bug was latent until commit aea49fbb01a ("target/i386: use gen_writeback()
within gen_POP()", 2024-06-08), and then became visible because gen_op_st_v
now receives op->ot instead of the "ot" returned by gen_pop_T0.

Analyzed-by: Clément Chigot <chigot@adacore.com>
Fixes: 5e9e21bcc4d ("target/i386: move 60-BF opcodes to new decoder", 2024-05-07)
Tested-by: Clément Chigot <chigot@adacore.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>