[MIPS] Make PAGE_OFFSET aware of PHYS_OFFSET

For platforms that use PHYS_OFFSET and do not use a mapped kernel,
this patch automatically adds PHYS_OFFSET into PAGE_OFFSET.
Therefore there are no more needs for them to redefine PAGE_OFFSET.

For mapped kernel, they need to redefine PAGE_OFFSET anyways.
Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

include/asm-mips/mach-generic/spaces.h

@@ -72,7 +72,7 @@
  * This handles the memory map.
  */
 #ifndef PAGE_OFFSET
-#define PAGE_OFFSET		CAC_BASE
+#define PAGE_OFFSET		(CAC_BASE + PHYS_OFFSET)
 #endif
 
 #endif /* __ASM_MACH_GENERIC_SPACES_H */