qemu: ARM emulation does not always get FPSCR exc flags right

Most of the ARM code to emulate Neon and VFP instructions gets the FPSCR cumulative exception flags correct; however there are still a few cases where we do not get these right. This is very minor stuff (nobody actually cares about the exception flags, especially when it's a matter of whether the Inexact flag got set or not) but it would be nice to actually tidy this up some day.

Mostly IIRC this is bugs in the softfloat code rather than target-arm itself.

Easiest way to find these is to run risu tests (we have patterns covering all of neon and vfp space) with the --test-fp-exc flag set.