media: vidtv: don't initialize cnr2qual var

As reported by gcc:

	drivers/media/test-drivers/vidtv/vidtv_demod.c: In function 'vidtv_demod_set_frontend':
	drivers/media/test-drivers/vidtv/vidtv_demod.c:265:42: warning: variable 'cnr2qual' set but not used [-Wunused-but-set-variable]
	  265 |  const struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
	      |                                          ^~~~~~~~

It turns that the var is not needed at all. So, just drop it.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>