EDAC, fsl_ddr: Add support for little endian

EDAC, fsl_ddr: Add support for little endian

Get endianness from device tree. Both big endian and little endian are
supported. Default to big endian for backwards compatibility to MPC85xx.

Signed-off-by: York Sun <york.sun@nxp.com>
Acked-by: Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: morbidrsa@gmail.com
Cc: oss@buserror.net
Cc: stuart.yoder@nxp.com
Link: http://lkml.kernel.org/r/1470779760-16483-7-git-send-email-york.sun@nxp.com
Signed-off-by: Borislav Petkov <bp@suse.de>