arm/dt: 8974: Update SPM sequences for Krait/L2

Update the SPM low power sequences per the hardware programming guide.
The SPM power colapse sequnce has been updated to remove any PLL related
SPM commands. The SPM can only control the HFPPLs and this could result
in HFPPL being turned on during power collapse if the Cores are running
off the global PLL.

Change-Id: I1e5ec93140cd82bd01d0d170b1ac574993eff277
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>