SystemUI: RAM bar view optimizations

findViewById() was being called every time updateSettings()
was being called. Instead, let's instantiate them once, and 
remove calls to updateSettings() since it will be called 
on its own when the setting values change.

Change-Id: Iaa02343caccb615921219be2a56b3bac4f3263b9
Signed-off-by: Roman Birg <romanbirg@gmail.com>
Merge "SystemUI: RAM bar view optimizations" into jb-mr1