[media] saa7134: Fix compilation breakage when go7007 is not selected

All error/warnings:

   drivers/built-in.o: In function `saa7134_go7007_fini':
>> saa7134-go7007.c:(.text+0x3b628b): undefined reference to `go7007_snd_remove'
   drivers/built-in.o: In function `saa7134_go7007_interface_reset':
>> saa7134-go7007.c:(.text+0x3b659a): undefined reference to `go7007_read_interrupt'
   drivers/built-in.o: In function `saa7134_go7007_init':
>> saa7134-go7007.c:(.text+0x3b65fa): undefined reference to `go7007_alloc'
>> saa7134-go7007.c:(.text+0x3b66ed): undefined reference to `go7007_boot_encoder'
>> saa7134-go7007.c:(.text+0x3b66fe): undefined reference to `go7007_register_encoder'
   drivers/built-in.o: In function `saa7134_go7007_irq_ts_done':
>> saa7134-go7007.c:(.text+0x3b6c2a): undefined reference to `go7007_parse_video_stream'
>> saa7134-go7007.c:(.text+0x3b6c86): undefined reference to `go7007_parse_video_stream'

This happens when:
 - VIDEO_SAA7134 is either 'm' or 'y'
 - VIDEO_GO7007 is not selected.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>