qos: Add support for PM_QOS_SUM type

PM_QOS_SUM is a new enum type supported in the upstream kernel. The target
qos value for PM_QOS_SUM type is updated as the sum of all the priorities
that are applicable to the current CPU.

Change-Id: I89152db4fbbf08db113b52e6c5fee4aba9b70933
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>