[POWERPC] QE: get rid of most device_types and model

Now we're searching for "fsl,qe", "fsl,qe-muram", "fsl,qe-muram-data"
and "fsl,qe-ic".

Unfortunately it's still impossible to remove device_type = "qe"
from the existing device trees because older u-boots are looking for it.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>