arm64: dts: mediatek: mt8395-genio-1200-evk: Disable unused backlight

arm64: dts: mediatek: mt8395-genio-1200-evk: Disable unused backlight

The builtin panel on the Genio 1200 EVK board uses the backlight_lcm0
node for its backlight. Though the backlight_lcd1 is currently left
enabled, it is unused, and its pwm input, disp_pwm1, is disabled, so it
fails probe. Disable this unused node.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20250502-genio-1200-disable-backlight-lcd1-v1-1-c021d2c9e48e@collabora.com
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>