soc: qcom: scm-mpu: Fix bug in unlock code path

The default behavior for xpus is to zero out the protected region when
it is unlocked. Pass a flag to the scm call to leave the memory region
unchanged.

Change-Id: Ib714d6db93bed2940006f8c0196b59da3fbd3161
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>