ARM: dts: msm: Add speed-bin 5 support for SDM439

Spyro derives its CPR configuration from SDM439. Add
CPR support for speed-bin 5 for Spyro.

While at it, update the CPR voltage step to 4mV to match
PMIC.

Change-Id: Ia2db2ed840a4ab9032366042f00a1a9ac086d912
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>