cpufreq: dt: Add support for hi3660

Add the compatible string for supporting the generic device tree cpufreq-dt
driver on Hisilicon's 3660 SoC.

Signed-off-by: Tao Wang <[e-mail]>
Acked-by: Viresh Kumar <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/cpufreq/cpufreq-dt-platdev.c

···
 	{ .compatible = "arm,integrator-ap", },
 	{ .compatible = "arm,integrator-cp", },
 
+	{ .compatible = "hisilicon,hi3660", },
 	{ .compatible = "hisilicon,hi6220", },
 
 	{ .compatible = "fsl,imx27", },