V4L/DVB (7242): ivtv: fix for yuv filter table check

As the result of a previous change that delayed the loading of the firmware,
the driver can sometimes report a bogus error regarding the yuv output filter
table not being found in the firmware. This patch moves the filter table
check to ensure it's only done after the firmware has been loaded.

Signed-off-by: Ian Armstrong <ian@iarmst.demon.co.uk>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>