msm: kgsl: Assign a default value to the variable ret

Currently there is a chance that the variable ret can be
used uninitialized in kgsl_reclaim_callback. Assign a default
value to ret to avoid this.

Change-Id: I90014370773ee2a6594ee624f890fead955e6f76
Signed-off-by: Puranam V G Tejaswi <quic_pvgtejas@quicinc.com>