Revert "media: dvb header files: move some headers to staging"

This reverts commit 819fbd3d

.

It turns out that some user-space applications use these uapi header
files, so even though the only user of the interface is an old driver
that was moved to staging, moving the header files causes unnecessary
pain.

Generally, we really don't want user space to use kernel headers
directly (exactly because it causes pain when we re-organize), and
instead copy them as needed.  But these things happen, and the headers
were in the uapi directory, so I guess it's not entirely unreasonable.

Link: https://lore.kernel.org/lkml/4e3e0d40-df4a-94f8-7c2d-85010b0873c4@web.de/
Reported-by: Soeren Moch <smoch@web.de>
Cc: stable@kernel.org  # 5.13
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>