HSI: ssi_protocol: avoid ssi_waketest call with held spinlock

This avoids calling ssi_waketest(), while a spinlock is
being hold, since ssi_waketest may sleep once irq_safe
runtime pm is disabled.

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