media: cx18: Fix incompatible type for argument error

media: cx18: Fix incompatible type for argument error

The first argument of function snd_ctl_new1 is of type const struct
snd_kcontrol_new * but in this file the variable is passed by value to
this function.
This generated ""incompatible type for argument" error. So, pass the
variable by reference.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>