HSI: omap_ssi_port: avoid calling runtime_pm_*_sync inside spinlock

runtime_pm_*_sync can block when irq_safe flag is removed
from omap-ssi driver, so it may not be called while a
spinlock is held.

Signed-off-by: Sebastian Reichel <sre@kernel.org>
Tested-by: Pavel Machek <pavel@ucw.cz>