soc: qcom: gladiator_erp_v2: initialize return value

Initialize the return value before it is used in the driver to
make sure valid return value is returned.

CRs-Fixed: 1050136
Change-Id: I3e2c524ac87d57ae33cd0f28b9c62b2a39ee79ad
Signed-off-by: Runmin Wang <runminw@codeaurora.org>