media: vidtv: fix some warnings

As reported by sparse:

	drivers/media/test-drivers/vidtv/vidtv_ts.h:47:47: warning: array of flexible structures
	drivers/media/test-drivers/vidtv/vidtv_channel.c:458:54: warning: incorrect type in argument 3 (different base types)
	drivers/media/test-drivers/vidtv/vidtv_channel.c:458:54:    expected unsigned short [usertype] service_id
	drivers/media/test-drivers/vidtv/vidtv_channel.c:458:54:    got restricted __be16 [usertype] service_id
	drivers/media/test-drivers/vidtv/vidtv_s302m.c:471 vidtv_s302m_encoder_init() warn: possible memory leak of 'e'

Address such warnings.

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