V4L/DVB (4419): Turn on the Low Noise Amplifier of the Samsung tuners.

Without the LNA these tuners perform very poorly (read 'unwatchable') when
the signal is weak.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>