Fix PV AAC decoder crash due to out-of-boundary array access.

Two cases were fixed:
o xover had a larger number of bands than the high frequency band, which led to some negative array index under some circumstances
o integrated a PV fix from OpenCore.git where the array index for scratch_mem may be over the array boundary

bug - 3473128

Change-Id: I844cd8797b4e5b0120fafa0c46a8c1facea78a8b