cxl: Isolate few psl8 specific calls

Point out the specific Coherent Accelerator Interface Architecture,
level 1, registers.
Code and functions specific to PSL8 (CAIA1) must be framed.

Signed-off-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
[mpe: Don't split long strings, it makes them hard to grep for]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>