crypto: qat - use u32 variables in all GEN4 pfvf_ops

Change adf_gen4_enable_vf2pf_interrupts() to use a u32 variable,
consistently with both other GEN4 pfvf_ops and pfvf_ops of other
generations.

Signed-off-by: Marco Chiappero <marco.chiappero@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>