xdma_device_open should not mutute channel_max

[hmaarrfk]

xilinx-dma-driver/xdma/libxdma.c

Line 3525 in 610e2fe

void *xdma_device_open(const char *mname, struct pci_dev *pdev, int *user_max,

Basically, this function returns a value and mutates something. This is super intuitive and should just return the handle of the device, and allow the calling function to update it's own cache.

To my knownledge, this is only called in one location, in

xdma/xdma_mod.c line 150.

I'm not going to fix this now because I have no way to test things...