linuxkpi: Define `DEFINE_XARRAY*()` macros

[dumbbell]

Summary

The DEFINE_XARRAY*() macros are used to declare a static xarray.

As the structure embeds a mutex(9), we also need to declare the static mutex after the struct xarray. Thus the slightly awkward definition of DEFINE_XARRAY_FLAGS().

The DRM generic code started to use DEFINE_XARRAY_ALLOC() in Linux 6.12.

This is part of the update of DRM drivers to Linux 6.12.

Sponsored by: The FreeBSD Foundation