MAINTAINERS: dmaengine: add files to Microchip dma entry

In Microchip DMA (HDMA actually) entry, add the missing files for
better matching with get_maintainer.pl tool.
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

MAINTAINERS

@@ -9512,6 +9512,8 @@ S:	Supported
 F:	drivers/dma/at_hdmac.c
 F:	drivers/dma/at_hdmac_regs.h
 F:	include/linux/platform_data/dma-atmel.h
+F:	Documentation/devicetree/bindings/dma/atmel-dma.txt
+F:	include/dt-bindings/dma/at91.h
 
 MICROCHIP / ATMEL ECC DRIVER
 M:	Tudor Ambarus <tudor.ambarus@microchip.com>