ice: Add input handlers for virtual channel handlers

Move the assignment to local variables after validation.

Remove unnecessary checks in ice_vc_process_vf_msg() as the respective
functions are now performing the checks.

Signed-off-by: "Amruth G.P" <amruth.gouda.parameshwarappa@intel.com>
Signed-off-by: Nitesh B Venkatesh <nitesh.b.venkatesh@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>