Move do_fixup* for libfdt into common code

Moved the generic fixup handling code out of cpu/mpc5xxx and cpu/mpc8260
into common/fdt_support.c and renamed:

do_fixup()	-> do_fixup_by_path()
do_fixup_u32() 	-> do_fixup_by_path_u32()

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

include/fdt_support.h

@@ -29,6 +29,10 @@
 #include <fdt.h>
 
 int fdt_chosen(void *fdt, ulong initrd_start, ulong initrd_end, int force);
+void do_fixup_by_path(void *fdt, const char *path, const char *prop,
+		      const void *val, int len, int create);
+void do_fixup_by_path_u32(void *fdt, const char *path, const char *prop,
+			  u32 val, int create);
 
 #ifdef CONFIG_OF_HAS_UBOOT_ENV
 int fdt_env(void *fdt);