PM / devfreq: memlat: add support for shared core-dev tables

A core-dev table is explicity defined in each memlat device
today. However, some devices may want to share the same core-dev
table so add support for parsing a shared core-dev table that
can be used across multiple memlat devices.

Change-Id: I5ee0d439c199a6414d2adaeed8328f3dc99b2a84
Signed-off-by: Amir Vajid <avajid@codeaurora.org>