Rename back to xt926, we will have kexec

Kexec will permit us to use this device tree with both developer and
consumer edition.

This reverts commit b4a42342a142f65f087376339955d0f40309b453.

Conflicts:
	device_xt926.mk

Change-Id: If6fd574749ea9c28dca2fc4f6f54f3594112a645