SystemUI: use matching padding on both sides of QS detail title

 * Add a paddingEnd for the title switch for
   left-to-right symmetry.

Test: visual observation
Change-Id: Ida3d238ffdf54bf1e6fa12e9a4b0a18168fb5aec
Signed-off-by: Timi Rautamäki <timi.rautamaki@gmail.com>