dmaengine: Add driver for Altera / Intel mSGDMA IP core

This driver adds support for the Altera / Intel modular Scatter-Gather
Direct Memory Access (mSGDMA) intellectual property (IP) to the Linux
DMAengine subsystem. Currently it supports the following op modes:

- DMA_MEMCPY
- DMA_SG
- DMA_SLAVE

This implementation has been tested on an Altera Cyclone FPGA connected
via PCIe, both on an ARM and an x86 platform.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>