Staging: vt6655: Fix do not use C99 // comments

Fix checkpatch.pl issues with do not use C99 //
comments in key.h

Signed-off-by: Yeliz Taneroglu <yeliztaneroglu@gmail.com>
Reviewed-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>