drm/xe/hw_engine_group: Avoid call kfree() for drmm_kzalloc()

Memory allocated with drmm_kzalloc() should not be freed using
kfree(), as it is managed by the DRM subsystem. The memory will
be automatically freed when the associated drm_device is released.
These 3 group pointers are allocated using drmm_kzalloc() in
hw_engine_group_alloc(), so they don't require manual deallocation.

Fixes: 67979060 ("drm/xe/hw_engine_group: Fix potential leak")
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/r/20250724193854.1124510-2-shuicheng.lin@intel.com