[media] [PATH,2/2] mxl5007 move loop_thru to attach

This patch move the loop_thru configuration to the attach function,
because with dual tuners until loop_tru configuration the other tuner
don't work.

Signed-off-by: Jose Alberto Reguero <jareguero@telefonica.net>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>