Fixing split shade going full black when changing density

The source of issue was status bar height defined in px while shelf height is defined in dp. When changing density, shelf height value in px decreases but status bar height remains the same. When density is low enough it means status bar height ends up bigger than shelf height and that messes up the calculation of NSSL's min expansion height.

Fixes: 210476328
Test: When having some notifications, change Display size to "Small" in settings -> expand split shade and check it's visible
Change-Id: I1e2506f9cf8b21f776a3698f58863ed868da07ba