[media] em28xx-video: simplify usage of the pointer to struct v4l2_ctrl_handler in em28xx_v4l2_init()

The local var hdl is already pointing to &dev->ctrl_handler.
Use it, instead of dereferencing it all the time.

Code cleanup. No functional changes.
Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>