bzip2/lzma: fix constant in decompress_inflate

Impact: Cleanup

Fix constant 0x8100 /* 32K */; according to Alain the value 0x8100 was
left over test code to test misalignment, the correct value is indeed
0x8000 == 32K.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>