vmkernel adapter which you want to designate for IP Storage, doesn't support Active-Active or Active-standby NIC teaming.
so all you got to do is, make sure you expose only one VMNIC to VMkernel port which you are created for IP storage on one of the vSwitches.
Let's say in following example, I have picked up my host with virtual switch vSwitch0, having only one VMNIC0, if I click on Properties of this virtual switch and add an additional VMKernel port, I will then be able to use it to do network port binding.
Note: If you have virtual switch with multiple uplink adapters, still you can do it, All you got to do in that case is, after addicting vmkernel adapter for IP Storage, please override nic teaming policy of that port and set only one VMNIC out of those multiple you have as active and push rest of those into unused adapters area.
that way your network port binding won't be troubled.
Let me know if this helps.