crypto: qat - do not handle PFVF sources for qat_4xxx

The QAT driver does not have support for PFVF interrupts for GEN4
devices, therefore report the vf2pf sources as 0.
This prevents a NULL pointer dereference in the function
adf_msix_isr_ae() if the device triggers a spurious interrupt.

Fixes: 993161d3 ("crypto: qat - fix handling of VF to PF interrupts")
Reported-by: Adam Guerin <adam.guerin@intel.com>
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>