V4L/DVB (7735): Fix compilation for au0828

Encountered this error when testing.

Kernel: arch/x86/boot/bzImage is ready  (#76)
  MODPOST 813 modules
ERROR: "dvb_dmx_init" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "dvb_unregister_adapter" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "dvb_register_frontend" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "dvb_unregister_frontend" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "dvb_net_release" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "dvb_frontend_detach" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "dvb_dmxdev_release" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "dvb_net_init" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "dvb_dmx_release" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "dvb_dmx_swfilter_packets" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "dvb_register_adapter" [drivers/media/video/au0828/au0828.ko] undefined!
ERROR: "dvb_dmxdev_init" [drivers/media/video/au0828/au0828.ko] undefined!
WARNING: modpost: Found 9 section mismatch(es).
To see full details build your kernel with:
'make CONFIG_DEBUG_SECTION_MISMATCH=y'
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

Signed-off-by: Brandon Philips <bphilips@suse.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>