msm: spm: add intermediate LPM mode for L2 PC

Currently when the core decide to enter into "PC + L2 PC"
LPM mode it informs to RPM and there is a chance of
system can enter into either XO or VDDmin. But this LPM
mode take longer time to enter and exit. Because of this
limitation some of the usecases where there is a less
latency APPS proc stays at lower LPM level (i.e GDFS) and
causing more power consumption. To address this issue adding
an intermediate LPM mode where L2 goes to PC but not inform
to RPM.

CRs-fixed: 552743
Change-Id: I321ff260d5baf8ac44917d67e9c9dfd260c8d5ca
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>