soc: qcom: pil: Use subsys_set_error to indicate firmware errors

Use subsys_set_error() to indicate invalid firmware image
that prevented subsystem from coming up. Userspace helper
applications will find this useful to take suitable
recovery action.

Change-Id: Ie03e4f2652692f30d32bbe80b39fb49ba95ea728
Signed-off-by: Meghana Ashok <meghanaa@codeaurora.org>