target/arm: Pack mtedesc into upper 32 bits of descriptor

target/arm: Pack mtedesc into upper 32 bits of descriptor

Instead of trying to pack mtedesc into the upper 17 bits of a 32-bit
gvec descriptor, pass the gvec descriptor in the lower 32 bits and
the mte descriptor in the upper 32 bits of a 64-bit operand.

This fixes two bugs:
 (1) in gen_sve_ldr() and gen_sve_str() call gen_mte_checkN() with a
 length value which is the SVE vector length and can be up to 256
 bytes. We don't assert there that it fits in the descriptor, so
 we would just fail to do the MTE checks on the right length of memory
 if the VL is more than 32 bytes

 (2) the new-in-SVE2p1 insns LD3Q, LD4Q, ST3Q, ST4Q also involve
 transfers of more than 32 bytes of memory. In this case we would
 assert at translate time.

(Note for potential backporting: this commit depends on the previous
"target/arm: Expand the descriptor for SME/SVE memory ops to i64".)

Fixes: 7b1613a1020d2942 ("target/arm: Enable FEAT_SME2p1 on -cpu max")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20250723165458.3509150-3-peter.maydell@linaro.org
[PMM: expand commit message to clarify that we are fixing bugs here]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>