soc: qcom: Add sysfs node to communicate with AOP using QMP protocol

This driver allows clients to send messages to Alway On processor
using QMP transport. Users can echo a frequency into an exposed sysfs
node to send to AOP. The driver expects the Cap frequency of DDR based
on SKU.

Change-Id: I083c1ec2da6990c5815550f897069ff27c6b7617
Signed-off-by: Vinay Sudra <vsudra@codeaurora.org>