msm: iomap: fsm9900: Add mapping for the MPM_PSHOLD region

Add an early mapping for the MPM PS_HOLD region to allow
the target to power down or reset.

Change-Id: I6acfdbecf39bfe94d6b26d39078d249832bb2a42
Acked-by: Kaushik Sikdar <ksikdar@qti.qualcomm.com>
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>