ARM: dts: msm: Vote for 681 MHz DDR for Fmax of all CPU speed bins

Change the mapping table of mincpubw to vote for 681MHz at the Fmax
of the lower speed bins of the CPUs.

Change-Id: Ie8b9abaceaa8585ab5b132076772b9c7ca71cbfe
Signed-off-by: Rohit Gupta <rohgup@codeaurora.org>