Remove abandonned capi support for the Mellanox CX4.

This reverts commit cbce0917.
Signed-off-by: NAlastair D'Silva <alastair@d-silva.org>
Acked-by: NAndrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>