IB/ehca: Include <linux/mutex.h> from ehca_classes.h

ehca_classes.h uses struct mutex, so while <linux/mutex.h> seems to be
pulled in indirectly by one of the headers it includes, the right
thing is to include <linux/mutex.h> directly.
Signed-off-by: Michael S. Tsirkin <mst@dev.mellanox.co.il>
Acked-by: Stefan Roscher <stefan.roscher@de.ibm.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/ehca/ehca_classes.h

@@ -53,6 +53,7 @@ struct ehca_pd;
 struct ehca_av;
 
 #include <linux/wait.h>
+#include <linux/mutex.h>
 
 #include <rdma/ib_verbs.h>
 #include <rdma/ib_user_verbs.h>