msm: pil: Delay after deasserting subsystem restart bits on 8974

The effects clearing *_RESTART registers are not immediate. A delay
is needed to ensure the subsystem is ready-to-go before registers
within it are manipulated. Fix this.

Change-Id: I12a996a7b5bf34c54a220aae90e8446f94dbdf8c
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>