Fix noodle SVE2 off by one bug (#309)

Fix noodle SVE2 off by one bug (#309)

By using svmatch on 16 bit lanes with a 8 bit predicate, we end up
including an undefined character in the pattern checks. The inactive
lane after load contains an undefined value, usually \0. Patterns
using \0 as the last character would then match this spurious
character, returning a match beyond the buffer's end. The fix checks
for such matches and rejects them.

Signed-off-by: Yoan Picchi <yoan.picchi@arm.com>