ARM: dts: msm: Set minimum CPUBW based on CPU freq

This allows setting a DDR frequency floor based on CPU frequency is
addition to using the bw_hwmon governor for decide the final CPU BW vote.
Because of how the BW votes are aggregated, if bw_hwmon pick a lower vote
than the floor, the final vote will be the floor value.

Change-Id: I281fbe9def75007629e5571e3bd6ceee598c7700
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>