Avoid processing LPC coeffs beyond the given order in NEON optimizations

Apply patch from https://git.xiph.org/?p=opus.git;a=commit;h=812ae3f

Bug: 138863511
Test: Verified builds for arm*
Change-Id: Ia5cc3e9be3372dcfddb4379a7afd135dbe6e21e0
1 file changed