target/arm: New function allocation_tag_mem_probe()

target/arm: New function allocation_tag_mem_probe()

For the FEAT_MOPS operations, the existing allocation_tag_mem()
function almost does what we want, but it will take a watchpoint
exception even for an ra == 0 probe request, and it requires that the
caller guarantee that the memory is accessible.  For FEAT_MOPS we
want a function that will not take any kind of exception, and will
return NULL for the not-accessible case.

Rename allocation_tag_mem() to allocation_tag_mem_probe() and add an
extra 'probe' argument that lets us distinguish these cases;
allocation_tag_mem() is now a wrapper that always passes 'false'.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230912140434.1333369-6-peter.maydell@linaro.org