ARM: dts: msm: Add an entry to the Silver memlat table for msm8998

Add a level at the lower end of the memlat table for the Silver
cluster so that the memlat driver votes for at least 200MHz
when the CPU's effective frequency is at most 300MHz for latency
bound workloads.

Change-Id: I2695d2d115d925ac8b274d93e59b2be6578f3001
Signed-off-by: Rohit Gupta <rohgup@codeaurora.org>