MAINTAINERS: add the linuppc-dev list to the fsl-mc bus entry

As discussed in the thread linked below, the fsl-mc bus lacked a clear
maintenance path. Since Christophe accepted to take the fsl-mc bus
patches through his soc fsl subtree, add the linuxppc-dev mailing list
in the MAINTAINERS entry.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Ioana Ciornei <[email protected]>
Acked-by: Christophe Leroy <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christophe Leroy <[email protected]>

Author: IoanaCiornei

MAINTAINERS

@@ -19295,6 +19295,7 @@ F:	include/linux/qnx6_fs.h
 
 QORIQ DPAA2 FSL-MC BUS DRIVER
 M:	Ioana Ciornei <[email protected]>
+L:	[email protected]
 L:	[email protected]
 S:	Maintained
 F:	Documentation/ABI/stable/sysfs-bus-fsl-mc