ice: check if VF exists before mode check

Setting trust on VF should return EINVAL when there is no VF. Move
checking for switchdev mode after checking if VF exists.

Fixes: c54d209c ("ice: Wait for VF to be reset/ready before configuration")
Signed-off-by: Michal Swiatkowski <michal.swiatkowski@intel.com>
Signed-off-by: Kalyan Kodamagula <kalyan.kodamagula@intel.com>
Tested-by: Sujai Buvaneswaran <sujai.buvaneswaran@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>