[PATCH] platform/chrome: cros_kbd_led_backlight: fix build warning

[Tzung-Bi Shih]

drivers/platform/chrome/cros_kbd_led_backlight.c got a new build warning
when using the randconfig in [1]:
>>> warning: unused variable 'keyboard_led_drvdata_ec_pwm'

The warning happens when CONFIG_CROS_EC is set but CONFIG_OF is not set.
Reproduce:
- mkdir build_dir
- wget [1] -O build_dir/.config
- COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 \
  O=build_dir ARCH=s390 SHELL=/bin/bash drivers/platform/chrome/

Fix the warning by hardening the guard condition.  Also use IS_ENABLED()
because CROS_EC is a tristate.

[1]: https://download.01.org/0day-ci/archive/20220717/202207170538.MR39dw8m-lkp@xxxxxxxxx/config

Fixes: 40f58143745e ("platform/chrome: cros_kbd_led_backlight: support EC PWM backend")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Tzung-Bi Shih <tzungbi@xxxxxxxxxx>
---
 drivers/platform/chrome/cros_kbd_led_backlight.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/platform/chrome/cros_kbd_led_backlight.c b/drivers/platform/chrome/cros_kbd_led_backlight.c
index 5ad41c10412d..4a0b2bd004d5 100644
--- a/drivers/platform/chrome/cros_kbd_led_backlight.c
+++ b/drivers/platform/chrome/cros_kbd_led_backlight.c
@@ -119,7 +119,7 @@ static const struct keyboard_led_drvdata keyboard_led_drvdata_acpi = {
 
 #endif /* CONFIG_ACPI */
 
-#ifdef CONFIG_CROS_EC
+#if IS_ENABLED(CONFIG_CROS_EC) && defined(CONFIG_OF)
 
 static int
 keyboard_led_set_brightness_ec_pwm(struct led_classdev *cdev,
@@ -187,11 +187,7 @@ static const struct keyboard_led_drvdata keyboard_led_drvdata_ec_pwm = {
 	.max_brightness = KEYBOARD_BACKLIGHT_MAX,
 };
 
-#else /* CONFIG_CROS_EC */
-
-static const struct keyboard_led_drvdata keyboard_led_drvdata_ec_pwm = {};
-
-#endif /* CONFIG_CROS_EC */
+#endif /* IS_ENABLED(CONFIG_CROS_EC) && defined(CONFIG_OF) */
 
 static int keyboard_led_probe(struct platform_device *pdev)
 {
-- 
2.37.0.170.g444d1eabd0-goog