drm/i915: use drm_printf() with the drm_err_printer intead of pr_err()

There's already a related drm_printer. Use it to preserve the context
instead of a separate pr_err().

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/246c0c275d05c919d959983e1784e3f7347f4540.1705410327.git.jani.nikula@intel.com