SystemUI: SearchPanelView: Optimize calculations

Only calculate if the screen is large once on initialization rather than every
time updateSettings() is called.

Change-Id: Ib54b6ef0ad6a987e75d6d98b5b269fc6e8f5104c
Merge pull request #17 from omnirom/android-4.4

SystemUI: SearchPanelView: Optimize calculations