Do not add quick settings padding to the content height when in split shade mode

We added a padding on top of the notifications for the quick settings even when in split shade mode (when quick settings on the left side). It resulted into increased scroll range. Fixed by not adding this padding when calculating content height in split shade mode.

Bug: 187298759
Test: open notifications when split shade mode enabled and
  when notifications content height is smaller than screen height,
  scroll notifications up => split shade should be closed
Change-Id: I49d7080153af2196ce78a88ac97e9aa4c8aab7e1