PM / devfreq: Don't hold spin lock when calling scm_call

Non atomic scm_call is being called for the new tz cmd ids.
This call for 64 bit support is single threaded, hence
don't hold a spinlock before calling it.

Change-Id: Ib19b2f6b5d62111395f4cae2197c3243d4a408ce
Signed-off-by: Suman Tatiraju <sumant@codeaurora.org>