ii2c: i2c-master-msm-geni: add null pointer check in event call back

Currently i2c geni driver doesn't have null pointer check condition
in event call back function. If any invalid event is coming from GSI,
i2c geni driver accessing null pointer which is causing crash.
To solve this added null pointer checks in event call back functions.

Change-Id: Ie14a40eee846c0ea29bec512d6320e9548c509b5
Signed-off-by: Anil Veshala Veshala <quic_aveshala@quicinc.com>
Signed-off-by: Mehul Raninga <quic_mraninga@quicinc.com>