Staging: vme: Replace semaphore by mutex.

Replace binary semaphore by mutex for code cleanup.
Mutex also gives better performance than semaphore.

Add 'mutex_destroy()' in 'vme_user_remove()' routine.

Signed-off-by: Santosh Nayak <santoshprasadnayak@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>