backlight: led_bl: Hold led_access lock when calling led_sysfs_disable()

backlight: led_bl: Hold led_access lock when calling led_sysfs_disable()

Lockdep detects the following issue on led-backlight removal:
  [  142.315935] ------------[ cut here ]------------
  [  142.315954] WARNING: CPU: 2 PID: 292 at drivers/leds/led-core.c:455 led_sysfs_enable+0x54/0x80
  ...
  [  142.500725] Call trace:
  [  142.503176]  led_sysfs_enable+0x54/0x80 (P)
  [  142.507370]  led_bl_remove+0x80/0xa8 [led_bl]
  [  142.511742]  platform_remove+0x30/0x58
  [  142.515501]  device_remove+0x54/0x90
  ...

Indeed, led_sysfs_enable() has to be called with the led_access
lock held.

Hold the lock when calling led_sysfs_disable().

Fixes: ae232e45acf9 ("backlight: add led-backlight driver")
Cc: stable@vger.kernel.org
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Link: https://lore.kernel.org/r/20250122091914.309533-1-herve.codina@bootlin.com
Signed-off-by: Lee Jones <lee@kernel.org>