sf: Don't do premultiplied alpha blending on the statusbar for hwc <= 0.3

Blending the translucent statusbar with the limited alpha implementation
of older HWC versions is glitch-prone, so don't do that with the compositor
at all

Change-Id: I96b49823b837a5063960d39c0937caea8bb3116a
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_frameworks_native into cd-4.4