crypto: qat - add NULL pointer check

There is a possibility that the function adf_devmgr_pci_to_accel_dev()
might return a NULL pointer.
Add a NULL pointer check in the function rp2srv_show().

Fixes: dbc8876d ("crypto: qat - add rp2svc sysfs attribute")
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Ahsan Atta <ahsan.atta@intel.com>
Reviewed-by: David Guckian <david.guckian@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/intel/qat/qat_common/adf_sysfs.c

@@ -215,6 +215,9 @@ static ssize_t rp2srv_show(struct device *dev, struct device_attribute *attr,
 	enum adf_cfg_service_type svc;
 
 	accel_dev = adf_devmgr_pci_to_accel_dev(to_pci_dev(dev));
+	if (!accel_dev)
+		return -EINVAL;
+
 	hw_data = GET_HW_DATA(accel_dev);
 
 	if (accel_dev->sysfs.ring_num == UNSET_RING_NUM)