arm: Fix handling of undefined instruction aborts in THUMB2 mode.

Correctly recognize NEON/SIMD and VFP instructions in THUMB2 mode and pass
these to the appropriate handler. Note that it is not necessary to filter
all undefined instruction variant or register combinations, this is a job
for given handler.

Reported by: Robert Clausecker <fuz@fuz.su>
PR: 259187
MFC after: 2 weks

(cherry picked from commit a670e1c13a522df4fb8c63bb023b88b1d65de797)
Signed-off-by: Olivier Houchard <cognet@FreeBSD.org>