Revert "Fix padding issue with lockscreen"

This reverts commit 5e8bc9d548af153e97b53d477e277a8ead6453f3.
Use RGB565 surface for wallpaper

Change-Id: I7db145882e7f84de5f0bd5e3991e96f929cb498c
Prefer 16bpp formats for opaque bitmaps

Change-Id: If9cf89d257b962d3c33ff4c1e5e29ad017ef092d