Update dma-proxy.c

[JoseFelipeFerrada]

I implemented a fix of a dma_proxy issue created by "class_create" modification here
following This forum

[Livius90]

It seems to me that there are no any maintainers for this repo, my PR is waiting for the review from 2023.
#8

[JoseFelipeFerrada]

Well... that sucks :c
Does xilinx has another way of interacting with AXI DMA in linux?

I hope this fix helps if anyone runs into the same error.