Revert "powerpc/powernv: Add support for the cxl kernel api on the real phb"

Remove abandonned capi support for the Mellanox CX4.

This reverts commit 4361b034.

Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>