Set dmc DRAM governor to performance on RK3399/default

https://forum.armbian.com/topic/7511-nanopi-m4/?do=findComment&comment=60848

packages/bsp/common/usr/lib/armbian/armbian-hardware-optimization

@@ -156,6 +156,10 @@ prepare_board() {
 			for i in $(awk -F':' 'tolower($0) ~ /pcie/{print $1}' </proc/interrupts | sed 's/\ //g'); do
 				echo 16 >/proc/irq/$i/smp_affinity
 			done
+			# set dmc memory governor to performance with default kernel
+			if [ -f /sys/bus/platform/drivers/rockchip-dmc/dmc/devfreq/dmc/governor ]; then
+				echo performance > /sys/bus/platform/drivers/rockchip-dmc/dmc/devfreq/dmc/governor
+			fi
 			;;
 		s500) # Roseapple Pi/LeMaker Guitar: send USB IRQs to cpu1/cpu2, DMA0 to cpu2 and Ethernet + SD card to cpu3
 			echo 2 >/proc/irq/$(awk -F":" "/usb1/ {print \$1}" </proc/interrupts | sed 's/\ //g')/smp_affinity