msm: spm: Allow setting of voltages across cpus

The original intent of disallowing voltage set across cpus is to prevent
setting of voltages on a core when its idle thread. The cpufreq
framework ensures that the frequency changes and hence the voltage
changes happens on the respective cpus. By allowing setting of voltages
from others cpus, the secondary cores can be brought out of reset by the
non-primary CPUs after boot and thereby help mitigate any thermal issues
associated wth multicores.

The regulator framework that calls into msm_spm_set_vdd provides the
necessary access restrictions to prevent simultaneous calls into
msm_spm_set_vdd.And hence the spinlocks around the set_vdd calls have
been removed.

Change-Id: Ie60673d4b65953a0a8f9ec9bafb82399f692a7b5
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>