crypto: qat - fix virtual channel configuration for GEN6 devices

crypto: qat - fix virtual channel configuration for GEN6 devices

The TCVCMAP (Traffic Class to Virtual Channel Mapping) field in the
PVC0CTL and PVC1CTL register controls how traffic classes are mapped to
virtual channels in QAT GEN6 hardware.

The driver previously wrote a default TCVCMAP value to this register, but
this configuration was incorrect.

Modify the TCVCMAP configuration to explicitly enable both VC0 and VC1,
and map Traffic Classes 0 to 7 → VC0 and Traffic Class 8 → VC1.
Replace FIELD_PREP() with FIELD_MODIFY() to ensure that only the intended
TCVCMAP field is updated, preserving other bits in the register. This
prevents unintended overwrites of unrelated configuration fields when
modifying TC to VC mappings.

Fixes: 17fd7514ae68 ("crypto: qat - add qat_6xxx driver")
Signed-off-by: Suman Kumar Chakraborty <suman.kumar.chakraborty@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>