MAINTAINERS: Add memory drivers to AT91 entry

Both atmel-ebi and atmel-sdram are maintained as part of the Atmel ARM
SoCs.
Suggested-by: NLee Jones <lee.jones@linaro.org>
Acked-by: NNicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

MAINTAINERS

@@ -1110,6 +1110,7 @@ F:	arch/arm/boot/dts/at91*.dtsi
 F:	arch/arm/boot/dts/sama*.dts
 F:	arch/arm/boot/dts/sama*.dtsi
 F:	arch/arm/include/debug/at91.S
+F:	drivers/memory/atmel*
 
 ARM/ATMEL AT91 Clock Support
 M:	Boris Brezillon <boris.brezillon@free-electrons.com>