drm/xe/kunit: Allow to replace xe_managed_bo_create_pin_map()

We want to use replacement functions in upcoming kunit tests.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241220194205.995-11-michal.wajdeczko@intel.com