rtc: pcf8563: Constify clkout_rates

The lates of clockout should be marked const. Make that so.
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Link: https://lore.kernel.org/r/20191108002449.15097-1-iwamatsu@nigauri.orgSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-pcf8563.c

@@ -390,7 +390,7 @@ static int pcf8563_irq_enable(struct device *dev, unsigned int enabled)
 
 #define clkout_hw_to_pcf8563(_hw) container_of(_hw, struct pcf8563, clkout_hw)
 
-static int clkout_rates[] = {
+static const int clkout_rates[] = {
 	32768,
 	1024,
 	32,