MAINTAINERS: add new entries for Armada 8K cpufreq driver

This new driver belongs to the mvebu family, update the MAINTAINER file
to document it.
Signed-off-by: NGregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

MAINTAINERS

@@ -1737,6 +1737,7 @@ F:	arch/arm/configs/mvebu_*_defconfig
 F:	arch/arm/mach-mvebu/
 F:	arch/arm64/boot/dts/marvell/armada*
 F:	drivers/cpufreq/armada-37xx-cpufreq.c
+F:	drivers/cpufreq/armada-8k-cpufreq.c
 F:	drivers/cpufreq/mvebu-cpufreq.c
 F:	drivers/irqchip/irq-armada-370-xp.c
 F:	drivers/irqchip/irq-mvebu-*