myri10ge: use DCA if DCA is compiled as a module

Use DCA in myri10ge when CONFIG_DCA_MODULE is set as well.

And thus force INTEL_IOATDMA to =y so that DCA=y if we are =y.

Signed-off-by: Brice Goglin <brice@myri.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>