ARM: dts: msm: enable rcu_expedited for rcu grace period in sdm670

To mitigate performance issues, set rcu_expedited=1,
so that expedited grace-period primitives can be used.

Change-Id: I7c7050c98875f2108cc932e89d6b4453742f8b27
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>