arch/tile: provide kernel support for the tilegx mPIPE shim

The TILE-Gx chip includes a packet-processing network engine called
mPIPE ("Multicore Programmable Intelligent Packet Engine").  This
change adds support for using the mPIPE engine from within the
kernel.  The engine has more functionality than is exposed here,
but to keep the kernel code and binary simpler, this is a subset
of the full API designed to enable standard Linux networking only.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

arch/tile/gxio/Kconfig

@@ -9,3 +9,9 @@ config TILE_GXIO
 config TILE_GXIO_DMA
 	bool
 	select TILE_GXIO
+
+# Support direct access to the TILE-Gx mPIPE hardware from kernel space.
+config TILE_GXIO_MPIPE
+	bool
+	select TILE_GXIO
+	select TILE_GXIO_DMA