misc: cxl: Use device_type helpers to access the node type

Remove directly accessing device_node.type pointer and use the accessors
instead. This will eventually allow removing the type pointer.

Cc: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>