smdk4412: don't use threaded vsync

The gralloc for smdk4412 waits for vsync. Having
threaded vsync in this case would be problematic
provided our gralloc implementation is different
from that of samsung.

Change-Id: I6c9a84c2bd00a43b47d86647829b9010367dca5d

Conflicts:
	arch/arm/configs/custom_i9300_defconfig