i40e: add input validation for virtchnl handlers

Change some data to unsigned int instead of integer when we compare.

Check LUT values in VIRTCHNL_OP_CONFIG_RSS_LUT handler.

Also enhance error/warning messages to print the real values of
I40E_MAX_VF_QUEUES, I40E_MAX_VF_VSI and I40E_DEFAULT_QUEUES_PER_VF
instead of plain text.

Refactor code to comply with 'check first then assign' policy.

Remove duplicate checks for VIRTCHNL_OP_CONFIG_RSS_KEY and
VIRTCHNL_OP_CONFIG_RSS_LUT opcodes in i40e_vc_process_vf_msg(). We have
the very same checks inside the handlers already.

Signed-off-by: Sergey Nemov <sergey.nemov@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>