RDMA/core: Add the function ib_mtu_int_to_enum

As the functionality to convert the MTU from a number to enum_ib_mtu
is ubiquitous, define a dedicated function and remove the duplicated
code.

Signed-off-by: Ram Amrani <Ram.Amrani@cavium.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
diff --git a/drivers/infiniband/hw/cxgb4/provider.c b/drivers/infiniband/hw/cxgb4/provider.c
index fa64f5d..3345e1c 100644
--- a/drivers/infiniband/hw/cxgb4/provider.c
+++ b/drivers/infiniband/hw/cxgb4/provider.c
@@ -373,16 +373,7 @@ static int c4iw_query_port(struct ib_device *ibdev, u8 port,
 
 	memset(props, 0, sizeof(struct ib_port_attr));
 	props->max_mtu = IB_MTU_4096;
-	if (netdev->mtu >= 4096)
-		props->active_mtu = IB_MTU_4096;
-	else if (netdev->mtu >= 2048)
-		props->active_mtu = IB_MTU_2048;
-	else if (netdev->mtu >= 1024)
-		props->active_mtu = IB_MTU_1024;
-	else if (netdev->mtu >= 512)
-		props->active_mtu = IB_MTU_512;
-	else
-		props->active_mtu = IB_MTU_256;
+	props->active_mtu = ib_mtu_int_to_enum(netdev->mtu);
 
 	if (!netif_carrier_ok(netdev))
 		props->state = IB_PORT_DOWN;