ARM: socfpga: support big endian for socfpga

Now the debug and platsmp.S are fixed for big endian, the
architecture can now advertise big endian support.
Signed-off-by: NBen Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: NDinh Nguyen <dinguyen@opensource.altera.com>

arch/arm/mach-socfpga/Kconfig

 config ARCH_SOCFPGA
 	bool "Altera SOCFPGA family" if ARCH_MULTI_V7
+	select ARCH_SUPPORTS_BIG_ENDIAN
 	select ARM_AMBA
 	select ARM_GIC
 	select CACHE_L2X0