V4L/DVB (4605): Fixes an issue with V4L1 and make headers-install

V4L1 support should be disabled when no CONFIG_VIDEO_V4L1_COMPAT is defined,
to allow checking for broken V4L2 ports. This is very important during the
migration phase for V4L2 API.
However, userspace apps should be capable of using both APIs, since they need
to test at runtime, via VIDIOCGCAP ioctl, if V4L1 is supported. So, when
__KERNEL__ is not defined, those ioctls and corresponding structs should be
visible.
This patch also removes the obsolete defines HAVE_V4L1 and HAVE_V4L2, that
where causing some confusion, and were replaced by CONFIG_VIDEO_V4L1_COMPAT
and CONFIG_VIDEO_V4L2.

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