soc/intel/apollolake: Move privilege drop to later stage

Previously privilege drop was happening "too early" and that caused some
PMC IPC programming (performed in FSP) to fail because sideband was
already locked out. This change set moves privilege drop to later stage,
after last FSP notify call.

BRANCH=reef
BUG=chrome-os-partner:60657
TEST=iotools rdmsr X 0x121, make sure they can't be read.
Also dmesg|grep -i IPC to make sure there are no errors related

Change-Id: Ia3a774aee5fbf92805a5c69093bfbd3d7682c3a7
Signed-off-by: Andrey Petrov <andrey.petrov@intel.com>
Reviewed-on: https://review.coreboot.org/17769
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/apollolake/Kconfig

@@ -36,6 +36,7 @@ config CPU_SPECIFIC_OPTIONS
 	select NO_FIXED_XIP_ROM_SIZE
 	select NO_XIP_EARLY_STAGES
 	select PARALLEL_MP
+	select PARALLEL_MP_AP_WORK
 	select PCIEXP_ASPM
 	select PCIEXP_COMMON_CLOCK
 	select PCIEXP_CLK_PM