msm: spm: set pc mode bit for SAW2_3.0

Set the power collapse bitin SAW2_SPM_CTL register.
This bit is used to differentiate other low power modes
from power collapse mode. This information is used for
contolling DBGWRDUP input signal. If PC_MODE is set DBGPWRDUP
signal is de-asserted as soon as SPM_WAIT_ACK becomes HIGH.
When the PC mode is not set it will help in early exit from
clock gating.

Change-Id: I74c44d3bb2b02bec449c809a5868ff944436eb09
Signed-off-by: Venkat Devarasetty <vdevaras@codeaurora.org>