tile: support new Tilera hypervisor

The Tilera hypervisor shipped in releases up through MDE 4.1 launches
the client operating system (i.e. Linux) at privilege level 1 (PL1).
Starting with MDE 4.2, as part of the work to enable KVM, the
Tilera hypervisor launches Linux at PL2 instead.

This commit makes the KERNEL_PL option default to 2 for tilegx, while
still saying at 1 for tilepro, which doesn't have an updated hypervisor.
It also explains how and when you might want to choose another value.
In addition, we change a small buglet in the on-chip Ethernet driver,
where we were failing to use the KERNEL_PL constant in an API call.

To make the transition cleaner, this change also provides the updated
hv_init() API for the new hypervisor that supports announcing Linux's
compiled-in PL, so the hypervisor can generate a suitable error in the
case of a mismatched hypervisor and Linux binary.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Cc: stable@vger.linux.org

drivers/net/ethernet/tile/tilegx.c

@@ -930,7 +930,7 @@ static int tile_net_setup_interrupts(struct net_device *dev)
 		if (info->has_iqueue) {
 			gxio_mpipe_request_notif_ring_interrupt(
 				&context, cpu_x(cpu), cpu_y(cpu),
-				1, ingress_irq, info->iqueue.ring);
+				KERNEL_PL, ingress_irq, info->iqueue.ring);
 		}
 	}