openrisc: include: asm: Kbuild: add default "vga.h"

Add default "vga.h", or compiling fails with 'allmodconfig'.

The related error:

    CC [M]  drivers/gpu/drm/drm_irq.o
  In file included from include/linux/vgaarb.h:34:0,
                   from drivers/gpu/drm/drm_irq.c:42:
  include/video/vga.h:22:21: fatal error: asm/vga.h: No such file or directory
  compilation terminated.
  make[3]: *** [drivers/gpu/drm/drm_irq.o] Error 1
  make[2]: *** [drivers/gpu/drm] Error 2
  make[1]: *** [drivers/gpu] Error 2
  make: *** [drivers] Error 2
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Jonas Bonn <jonas@southpole.se>

arch/openrisc/include/asm/Kbuild

@@ -65,5 +65,6 @@ generic-y += trace_clock.h
 generic-y += types.h
 generic-y += ucontext.h
 generic-y += user.h
+generic-y += vga.h
 generic-y += word-at-a-time.h
 generic-y += xor.h