ARM: dts: msm: Move LD8 and S4 to stub regulators in fsm9900

Add stub regulators for LDO8 and S4 in all FSM9900 targets. They
are configured and controlled by TZ or SBL.

Change-Id: I96c6761542a3154371ac4aefc5519ff9b3f663a4
Acked-by: Jie Luo <jluo@qti.qualcomm.com>
Signed-off-by: Gilad Avidov <gavidov@codeaurora.org>