expressatt: Wait for kgsl nodes in early init

4 times out of 5, /dev/kgsl-* isn't ready by the time surfaceflinger
starts, so adreno libraries fail to load properly. This causes a blank
screen during most of boot. Wait for dev/kgsl-3d0 to become ready before
proceeding.

Change-Id: Iad211e8a3e19913f664fa5234c91aa40b287ff82