fs: btrfs: Fix unaligned memory accesses

Loading files stored with lzo compression from a btrfs filesystem was
producing unaligned memory accesses, which were causing a data abort
and a reset on an Orange Pi Zero.

The change in hash.c is not triggered by any error but follows the
same pattern. Please confirm.

Fixed according to doc/README.unaligned-memory-access.txt

Signed-off-by: Alberto Sánchez Molero <alsamolero@gmail.com>
Tested-by: Robert Nelson <robertcnelson@gmail.com>