m68k: define 'VM_DATA_DEFAULT_FLAGS' no matter whether has 'NOMMU' or not

Define 'VM_DATA_DEFAULT_FLAGS' when 'NOMMU' to pass compiling.

So move it from "include/asm/page_mm.h to "include/asm/page.h"

The related make:

  make ARCH=m68k randconfig
  make ARCH=m68k menuconfig
    choose cross compiler
    disable MMU support
  make ARCH=m68k V=1 EXTRA_CFLAGS=-W

The related error:

  security/selinux/hooks.c: In function ‘selinux_init’:
  security/selinux/hooks.c:5821:21: error: ‘VM_DATA_DEFAULT_FLAGS’ undeclared (first use in this function)

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>