soc: qcom: spm: Split SPM/AVS functionality

SPM DT node supplies all the register information and expects
initialization value for all of them. With PSCI, most of the SPM
programming will be done in EL1 secure and only vctl programming will be
done from HLOS. Change the spm driver to allow write to only those
registers which has initialization values provided in DT.

Change-Id: I073c1c0487bfa98400e234e32f1cc27f20f3b79e
Signed-off-by: Archana Sathyakumar <asathyak@codeaurora.org>
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>