msm: spm: Unify SPM enums for power modes

Unify the SPM enums for power modes across multiple devices. This
prevents the driver from having to maintain different tables to support
multiple SPM devices in the system. Currently, only two types of SPM
devices are supported, cpu and L2, but multiple such SPM devices could
be available on newer targets.

Change-Id: I89305bee79ca8a1560f9ea1b81e241713a43c8ab
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>