MAINTAINERS: Add entry for drivers/platform/mips/

Add drivers/platform/mips to the MIPS architecture MAINTAINERS entry.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
[jhogan@kernel.org: Expand commit message]
Signed-off-by: James Hogan <jhogan@kernel.org>

MAINTAINERS

@@ -9096,6 +9096,7 @@ S:	Supported
 F:	Documentation/devicetree/bindings/mips/
 F:	Documentation/mips/
 F:	arch/mips/
+F:	drivers/platform/mips/
 
 MIPS BOSTON DEVELOPMENT BOARD
 M:	Paul Burton <paul.burton@mips.com>