drm: arm: malidp: Don't destroy planes manually in error handlers

The top-level error handler calls drm_mode_config_cleanup() which will
destroy all planes. There's no need to destroy them manually in lower
error handlers.

As plane cleanup is now handled entirely by drm_mode_config_cleanup(),
we must ensure that the plane .destroy() handler frees allocated memory
for the plane object that was freed by malidp_de_planes_destroy(). Do so
by replacing the call to devm_kfree() in the .destroy() handler by
kfree(). devm_kfree() is currently a no-op as the plane memory is
allocated with kzalloc(), not devm_kzalloc().

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>