Staging: sxg: clean up C99 comments

Change  C99 comments to C89 comments

Some nested comments seem to have been missed and some blocks are redundantly
commented, but at least most of the //'s are gone

Signed-off by: J.R. Mauro <jrm8005@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>