V4L/DVB (10176a): Switch remaining clear_user_page users over to clear_user_highpage

Not all architectures provide clear_user_page(), but clear_user_highpage()
is available everywhere at least via the compatibility inline function.

Is this the "trivial patch" that's required for these two drivers?

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>