V4L/DVB: cx25821: Make comments C99 compliant

Replace all // comments by /* */

Patch generated with this small script:

	for i in drivers/staging/cx25821/*.[ch]; do cat $i|perl -ne 's,//\s*(.*)\s*\n,/* $1 */\n,g; print $_;' >a && mv a $i; done

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>