dma: MIC X100 DMA Driver

This patch implements DMA Engine API for DMA controller on MIC X100
Coprocessors. DMA h/w is shared between host and card s/w.
Channels 0 to 3 are used by host and 4 to 7 are used by card.
Since the DMA device doesn't show up as PCIe device, a virtual bus called mic
bus is created and virtual devices are added on that bus to follow device model.
Allowed dma transfer directions are host to card, card to host and card to card.

Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Reviewed-by: Nikhil Rao <nikhil.rao@intel.com>
Reviewed-by: Sudeep Dutt <sudeep.dutt@intel.com>
Signed-off-by: Siva Yerramreddy <yshivakrishna@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>