[media] gspca/kinect: wrap gspca_debug with GSPCA_DEBUG

Fixes media_build, and presumably certain other upstream kernel build
option combos.

Before:
  CC [M]  /home/jarod/src/media_build/v4l/kinect.o
/home/jarod/src/media_build/v4l/kinect.c:38:19: error: 'D_ERR' undeclared here (not in a function)
/home/jarod/src/media_build/v4l/kinect.c:38:27: error: 'D_PROBE' undeclared here (not in a function)
/home/jarod/src/media_build/v4l/kinect.c:38:37: error: 'D_CONF' undeclared here (not in a function)
/home/jarod/src/media_build/v4l/kinect.c:38:46: error: 'D_STREAM' undeclared here (not in a function)
/home/jarod/src/media_build/v4l/kinect.c:38:57: error: 'D_FRAM' undeclared here (not in a function)
/home/jarod/src/media_build/v4l/kinect.c:38:66: error: 'D_PACK' undeclared here (not in a function)
/home/jarod/src/media_build/v4l/kinect.c:39:2: error: 'D_USBI' undeclared here (not in a function)
/home/jarod/src/media_build/v4l/kinect.c:39:11: error: 'D_USBO' undeclared here (not in a function)
/home/jarod/src/media_build/v4l/kinect.c:39:20: error: 'D_V4L2' undeclared here (not in a function)
make[3]: *** [/home/jarod/src/media_build/v4l/kinect.o] Error 1

After:
  CC [M]  /home/jarod/src/media_build/v4l/kinect.o
  ...
  LD [M]  /home/jarod/src/media_build/v4l/gspca_kinect.ko
  ...
  profit

Reported-by: Nicolas Will <nico@youplala.net>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>