PiP: Use vertical/horizontal padding base on PiP orientation.

Since not all paddings are created the same, let's respect the correct
top/bottom or left/right pair based on PIP orientation.

Bug: 187525862
Test: Open vertical PIP, rotate to landscape, maximize PIP - respects
maximum space now

Change-Id: Ib04ac72328e246302b45fe6630dc01d0c081cfcc