oxnas: use ARM BCJ filter for XZ decompression

Restoring the config for kernel 3.14 didn't contain that change already
made to config-3.18.
It is needed to make squashfs in the kernel match the compression settings
for ARCH=arm in the framework.
If set to ARMTHUMB, boot fails due to squashfs being unreadable if the
filesystem was generated for wth ARM BCJ filter.

in include/image.mk:    BCJ_FILTER:=-Xbcj $(LINUX_KARCH)
Thus the ARM filter is used for all ARM targets.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

SVN-Revision: 43640