Update xdna-driver and XRT version to succeed compiling with real 6.8

[keryell]

The XRT required in the git submodule is too old to compile with 6.8 but at the same time this driver does not compile with XRT of the day.

[maxzhen]

We'll update XRT git submodule later. For now, the compilation failure of the XRT driver can be ignored.

[keryell]

The situation is complicated at least, since there are a few bugs in XRT currently. :-(
Need to wait for Xilinx/XRT#8046 to land.

[keryell]

I have added an easy one to avoid breaking systems with pre-6.8 kernels #32

[keryell]

Done by #34 and #35