drm/i915/debugfs: clean up LPSP capable

Clean up the LPSP capability printout. No functional changes.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/097390f12da8de57c9d52ad675309d0422dec8fb.1630327990.git.jani.nikula@intel.com