netdev: ehea: ehea_fw_handles semaphore to mutex

Converted the ehea_fw_handles.lock to a mutex.

Signed-off-by: Daniel Walker <dwalker@mvista.com>
Cc: Christoph Raisch <raisch@de.ibm.com>
Cc: Jan-Bernd Themann <themann@de.ibm.com>
Cc: Thomas Klein <tklein@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>