media: dw9714: Remove client field in driver's struct

The client field in driver's struct is redundant. Remove it.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Tested-by: Rajmohan Mani <rajmohan.mani@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>