[patch, -git] drivers/media build fix for modular builds

[Ingo Molnar <mingo@elte.hu>]

fix allmodconfig build bug introduced in latest -git by commit 
7c91f0624a9 ("V4L/DVB(7767): Move tuners to common/tuners"):

  LD      kernel/built-in.o
  LD      drivers/built-in.o
  ld: drivers/media/built-in.o: No such file: No such file or directory

which happens if all media drivers are modular:

  http://redhat.com/~mingo/misc/config-Wed_Apr_30_09_24_48_CEST_2008.bad

In that case there's no obj-y rule connecting all the built-in.o files and
the link tree breaks.

the fix is to add a guaranteed obj-y rule for the core vmlinux to build.
(which results in an empty object file if all media drivers are modular)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 drivers/media/Makefile |    2 ++
 1 file changed, 2 insertions(+)

Index: linux/drivers/media/Makefile
===================================================================
--- linux.orig/drivers/media/Makefile
+++ linux/drivers/media/Makefile
@@ -2,6 +2,8 @@
 # Makefile for the kernel multimedia device drivers.
 #
 
+obj-y := common/
+
 obj-$(CONFIG_VIDEO_MEDIA) += common/
 
 # Since hybrid devices are here, should be compiled if DVB and/or V4L