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>