platform/chrome: cros_kbd_led_backlight: Remove CROS_EC dependency

platform/chrome: cros_kbd_led_backlight: Remove CROS_EC dependency

After applying 3a1d61dc3202 ("platform/chrome: cros_kbd_led_backlight:
Remove OF match"), cros_kbd_led_backlight no longer depends on CROS_EC
directly.

Remove the redundant dependency.

Fixes: 3a1d61dc3202 ("platform/chrome: cros_kbd_led_backlight: Remove OF match")
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20250414132427.204078-2-tzungbi@kernel.org
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>