Staging: cxt1e1: rename global log_level variable

The driver should not have such a generic global variable name.

Reported-by: Zimny Lech <napohybelskurwysynom2010@gmail.com>
Cc: Bob Beers <bob.beers@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>