power: supply: ab8500: Add MAINTAINERS entry

I am maintaining these drivers so add patterns to MAINTAINERS
for them.

Signed-off-by: Linus Walleij <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>

MAINTAINERS

···
 F:	Documentation/scsi/aacraid.rst
 F:	drivers/scsi/aacraid/
 
+AB8500 BATTERY AND CHARGER DRIVERS
+M:	Linus Walleij <[e-mail]>
+F:	Documentation/devicetree/bindings/power/supply/*ab8500*
+F:	drivers/power/supply/*ab8500*
+
 ABI/API
 L:	[e-mail]
 F:	include/linux/syscalls.h