release: arm64: rockpro64: Set hw.ncpu to 4

Since there is known issue with big.LITTLE set the number of CPU to 4
which is the number present in the LITTLE cluster.

release/arm64/ROCKPRO64.conf

@@ -26,3 +26,10 @@ arm_install_uboot() {
 		of=/dev/${mddev} bs=512 seek=16384 conv=sync
 	return 0
 }
+
+arm_do_quirk() {
+	echo '# Known issue with big.LITTLE' \
+		>> ${CHROOTDIR}/${DESTDIR}/boot/loader.conf
+	echo 'hw.ncpu=4' \
+		>> ${CHROOTDIR}/${DESTDIR}/boot/loader.conf
+}