soc: qcom: subsys_notif: Add early SSR notifications for PCIe DRV

PCIe DRV needs to recover the link as soon as possible before
the device on the other side of the link times out. Allow PCIe
DRV to register for early SSR notifications to have a chance of
making the recovery latency.

Change-Id: I75ce59075efcebc7c4457d300f7558b837d725a0
Signed-off-by: Tony Truong <truong@codeaurora.org>