ARM: 8165/1: alignment: don't break misaligned NEON load/store

The alignment fixup incorrectly decodes faulting ARM VLDn/VSTn
instructions (where the optional alignment hint is given but incorrect)
as LDR/STR, leading to register corruption. Detect these and correctly
treat them as unhandled, so that userspace gets the fault it expects.

Change-Id: I0848bac77eee63531cc5300fda38fbb9390e3193
Reported-by: Simon Hosie <simon.hosie@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>