ARM: dts: msm: enable bwmon4 for cpubw monitor for msmcobalt

Add the qcom,hw-timer-hz property and enable qcom,bimc-bwmon4
device for msmcobalt to be able to use the BWMON2 hardware
instead of the legacy BWMON hardware.

Change-Id: I1d1c2e5d2fcf705d8ffd527ec7434d90cc004834
Signed-off-by: David Keitel <dkeitel@codeaurora.org>