firmware: arm_scmi: replace of_match_device->data with of_device_get_match_data()

of_match_device can return NULL if no matching device is found though
it's highly unlikely to happen in scmi_probe as it's called only if
a valid match is found.

However we can use of_device_get_match_data() instead of
of_match_device()->data to handle NULL pointer checks and return -EINVAL
in such a scenario.

Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Aditya Pakki <pakki001@umn.edu>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>