cxl: Remove abandonned capi support for the Mellanox CX4, final cleanup

Remove a few XSL/CX4 oddities which are no longer needed. A simple
revert of the initial commits was not possible (or not worth it) due
to the history of the code.

Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>