MAINTAINERS: cxl: update maintainership

As Ian's stepping down from his maintainer role now that he's leaving IBM,
Frederic has asked me to add myself to the cxl maintainer list. Updating
accordingly.

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

MAINTAINERS

@@ -3722,6 +3722,7 @@ F:	drivers/net/ethernet/chelsio/cxgb4vf/
 
 CXL (IBM Coherent Accelerator Processor Interface CAPI) DRIVER
 M:	Frederic Barrat <fbarrat@linux.vnet.ibm.com>
+M:	Andrew Donnellan <andrew.donnellan@au1.ibm.com>
 L:	linuxppc-dev@lists.ozlabs.org
 S:	Supported
 F:	arch/powerpc/platforms/powernv/pci-cxl.c