[media] radio-si470x-i2c: fix a warning on ia64

on ia64, those warnings appear:
drivers/media/radio/si470x/radio-si470x-i2c.c:470:12: warning: 'si470x_i2c_suspend' defined but not used [-Wunused-function]
drivers/media/radio/si470x/radio-si470x-i2c.c:487:12: warning: 'si470x_i2c_resume' defined but not used [-Wunused-function]
They're caused because the PM logic uses this define:
#define SET_SYSTEM_SLEEP_PM_OPS()
With is only defined for CONFIG_PM_SLEEP.
So, change the logic there to test for CONFIG_PM_SLEEP, instead of
CONFIG_PM.

Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Reviewed-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/radio/si470x/radio-si470x-i2c.c

···
 }
 
 
-#ifdef CONFIG_PM
+#ifdef CONFIG_PM_SLEEP
 /*
  * si470x_i2c_suspend - suspend the device
  */
···
 	.driver = {
 		.name		= "si470x",
 		.owner		= THIS_MODULE,
-#ifdef CONFIG_PM
+#ifdef CONFIG_PM_SLEEP
 		.pm		= &si470x_i2c_pm,
 #endif
 	},