[media] cx25821-audio.h: Fix multiline defines

Change column of line continuation character ('\') and fix indent of
multiline defines.
Also line up remaining constant defines.

Signed-off-by: Leonid V. Fedorenchik <leonidsbox@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>