media: dvb-usb: Add helper macros for using USB VID/PID

In order to use designated initializers and to avoid avoid big lines
at the USB ID tables, define some helper macros.

Link: https://lore.kernel.org/linux-media/f82e376dea2e9b922f51a03d1e7730b03e49cc7d.1648499509.git.mchehab@kernel.org


Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>