staging: frontier: switch semaphores to mutexes

This patch changes the use of semaphores in alphatrack.c and tranzport.c to
mutexes at the suggestion of checkpatch.pl

Signed-off-by: Eli Lindsey <eli@siliconsprawl.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>