ARM: dts: msm: remove PoN node for pmi8994

PoN module is available on both pm8994 and pmi8994.
Pm8994 has master PoN module and used for power key
and other regular operations. Remove PoN device node
from pmi8994.

Change-Id: Ifa9239ccff61bf23f02740a48f1e53c0f558cba4
Signed-off-by: Mohan Pallaka <mpallaka@codeaurora.org>