AArch64: Fix instability in AdvSIMD sinh

AArch64: Fix instability in AdvSIMD sinh

Previously presence of special-cases in one lane could affect the
results in other lanes due to unconditional scalar fallback. The old
WANT_SIMD_EXCEPT option (which has never been enabled in libmvec) has
been removed from AOR, making it easier to spot and fix
this. No measured change in performance. This patch applies cleanly as
far back as 2.41, however there are conflicts with 2.40 where sinh was
first introduced.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>