drm/i915: Prefer '%ps' for printing function symbol names

%pS includes the offset, which is useful for return addresses but noise
when we are pretty printing a known (and expected) function entry point.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200319091943.7815-1-chris@chris-wilson.co.uk