gpu/buddy: Introduce gpu_buddy_assert() for kunit-aware assertions

gpu/buddy: Introduce gpu_buddy_assert() for kunit-aware assertions

Introduce gpu_buddy_assert(), a small helper that wraps WARN_ON() and,
when CONFIG_KUNIT is enabled, also calls kunit_fail_current_test() so
that any active KUnit test is marked as failed. In non-KUnit builds
the macro reduces to WARN_ON(), preserving existing behaviour.

Stringify the asserted condition in the failure message to make it easy
to identify which assertion fired. Leave the WARN_ON() in
gpu_buddy_block_trim() unchanged, as it returns -EINVAL and the caller
already observes the failure via the return code.

Cc: Christian König <christian.koenig@amd.com>
Cc: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Suggested-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Sanjay Yadav <sanjay.kumar.yadav@intel.com>
Reviewed-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Link: https://patch.msgid.link/20260227130037.53615-2-sanjay.kumar.yadav@intel.com