i40e/i40evf: restrict VC opcodes to their initial values

Until the time a more robust versioning scheme is needed/implemented all
established virtual channel opcode values should remain consistent between
updates to the opcode enum.

This patch repositions I40E_VIRTCHNL_OP_CONFIG_RSS to the end of the enum. In
its current position this opcode displaces the initial value of
I40E_VIRTCHNL_OP_EVENT and will cause PF/VF compatibility issues.

Going forward the expectation is either:
	a) All future opcode additions will be added as the last element of the
	enum. Once VF drivers start making use of the new commands the virtual
	channel version will need to be incremented and drivers will need to
	implement a simple version check whereby VF drivers can only load on
	PFs with a >= version.
	b) or, if needed, design and implement a more complicated API
	negotiation capability.

In either case PF drivers should always maintain backwards compatibility with
earlier VF driver versions.

Change-ID: Ie245daa09a231b6680ed793d648bdcc76caefe58
Signed-off-by: Nicholas Nunley <nicholas.d.nunley@intel.com>
Tested-by: Jim Young <james.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>