video: adf: define constants for device-custom ioctls

Device-custom ADF ioctls can use type ADF_IOCTL_TYPE and
nr >= ADF_IOCTL_NR_CUSTOM

Change-Id: Ia8270973df5100e996ca0e021ede60e54b9af72a
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Git-commit: c10c64d40bf14ce5964300991744d17296d57481
Git-Repo: https://android.googlesource.com/kernel/common.git


Signed-off-by: Ian Maund <imaund@codeaurora.org>