V4L/DVB (7195): xc5000: fix build error when built as module

drivers/built-in.o: In function `set_type':
tuner-core.c:(.text+0x8879d): undefined reference to `xc5000_attach'

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Reviewed-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>