MAINTAINERS: memory: cover also header file

Add include/memory/ in memory drivers maintainers entry.  So far there
is only one file there for Renesas Reduced Pin Count Interface driver.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210601160608.312446-2-krzysztof.kozlowski@canonical.com

MAINTAINERS

@@ -11796,6 +11796,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux-mem-ctrl.git
 F:	Documentation/devicetree/bindings/memory-controllers/
 F:	drivers/memory/
 F:	include/dt-bindings/memory/
+F:	include/memory/
 
 MEMORY FREQUENCY SCALING DRIVERS FOR NVIDIA TEGRA
 M:	Dmitry Osipenko <digetx@gmail.com>