Decreasing notifications height on split shade lockscreen

Notifications were taking too much space, sometimes overlapping with other lockscreen elements under it.
The issue was caused by notifications position calculation on lockscreen not always taking into account different arrangement in split shade, where notifications are not under keyguard status.

Fixes: 200838082
Test: 1. KeyguardClockPositionAlgorithmTest
2. Have a lot of notifications and see if they overlap other lockscreen elements

Change-Id: Ibbee12a85dc27e33726d206684a2120a99cfc42f