libhost1x: Display backend selection

Display the detected kernel interface while probing. While at it, remove
some of the more verbose output which isn't terribly useful anymore.

Signed-off-by: Thierry Reding <thierry@gilfi.de>
libhost1x: Update copyright headers

Some of the files were completely missing copyright headers. Remove
Avionic Design GmbH from the copyright holders, none of the libhost1x
code was written on the job.

Signed-off-by: Thierry Reding <thierry@gilfi.de>
libgrate: Remove duplicate nvhost implementation

This functionality is now abstracted behind the libhost1x API and the
duplicate implementation can be removed.

Signed-off-by: Thierry Reding <thierry@gilfi.de>