Alternate driver for Avalon-MM DMA for PCIe

My tests show that reading speed from FPGA memory to user-space memory is only 28MB/sec with IOCTL_AVALON_DMA_READ command. Other commands like IOCTL_*_SG and IOCTL_*_SG_SMP crashed for me, therefore I couldn't test them.

On our device (iMX8M-Plus and Arria 10 GX), the PCIe bus has 1 lane and the link trained at Gen3 speed. Previously I have tested the speed using AN690 mentioned above and it was about 300MB/sec on the same hardware. But in that case the Altera's application test software just keeps the data in the kernel and never transfers it to user space.

I have just realized that you have more updated code in avalon-dmaengine-v5.7-rc1 branch instead of avalon-dma-engine branch. I will test that as well to see if there are any improvements at reliability and speed.