drm/xe: Move and export xe_hw_engine lookup.

Move and export xe_hw_engine lookup. This is in preparation
to use this in eudebug code where we want to find active
engine.

v2: s/tile/gt due to uapi changes (Mika)

Signed-off-by: Dominik Grzegorzek <dominik.grzegorzek@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240729130152.100130-1-mika.kuoppala@linux.intel.com