drivers/misc/apds990x.c: apds990x_chip_on() should depend on CONFIG_PM || CONFIG_PM_RUNTIME

Fixes this warning:

  drivers/misc/apds990x.c: At top level:
  drivers/misc/apds990x.c:613: warning: `apds990x_chip_on' defined but not used
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Samu Onkalo <samu.p.onkalo@nokia.com>
Cc: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/misc/apds990x.c

@@ -609,6 +609,7 @@ static int apds990x_detect(struct apds990x_chip *chip)
 	return ret;
 }
 
+#if defined(CONFIG_PM) || defined(CONFIG_PM_RUNTIME)
 static int apds990x_chip_on(struct apds990x_chip *chip)
 {
 	int err	 = regulator_bulk_enable(ARRAY_SIZE(chip->regs),
@@ -624,6 +625,7 @@ static int apds990x_chip_on(struct apds990x_chip *chip)
 	apds990x_mode_on(chip);
 	return 0;
 }
+#endif
 
 static int apds990x_chip_off(struct apds990x_chip *chip)
 {