Revert "sync: clean up compiler warnings"

This reverts commit 1f01be32e992aed8ab1a08dba66840541eba0e13.
Revert "Revert "enable CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS""

This reverts commit cecbce837bc12745d76359635e426d4d12dec390.
staging: zram: change default selection of LZO compression to LZ4 as we don't use LZO compression anymore

NOTE: ZRAM needs another workaround. XVMALLOC includes backported driver from 3.7 kernel, so we must update the ZRAM driver to avoid conflicts. The current setup causes freezes.