msm: spm_devices: Support querying of spm devices by name

The current driver assumes that hardware has SPM devices to control CPU and
a L2 only. This restriction doesn't apply to all targets and so adding for
power modules to query spm devices by name to allow multiple spm devices
within the subsystem.

Also, added a new property qcom,cpu which references a CPU's phandle. The
driver will use the phandle to determine the logical CPU map instead if
relying on the qcom,core-id property. qcom,core-id property will be
supported on targets that doesn't support the CPU phandle but would
eventually be deprecated when all the targets have migrated over to
defining CPU phandles.

Also, remove any used APIs in the process.

Change-Id: I3a89fa164d00b91d52f26c6a373af7188cb7908c
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>