ANDROID: squashfs: Fix endianness issue

Code in squashfs_process_blocks was not correctly assigning
length. Casting to u16* introduced endianness issues on some
architectures.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Bug: 35257858
Change-Id: I9efaef4bc531b7469de79cf94738ade2dd6e6a8c