regulator: spm_regulator: Add snapshot of spm_regulator driver

This is snapshot of the spm_regulator driver as of msm-4.4
'commit 26efcc23eb82 ("regulator: spm: check min/max voltages
against HW configuration")'.

Also replace the __invoke_psci_fn_smc wrapper with arm_smccc_smc as
__invoke_psci_fn_smc is no longer available.

Change-Id: Ia6ded6dc21ecff2114ddd20e26706d9196239956
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>