pwm: mtk-disp: Don't check the return code of pwmchip_remove()

[ Upstream commit 9b7b5736ffd5da6f8f6329ebe5f1829cbcf8afae ]

pwmchip_remove() returns always 0. Don't use the value to make it
possible to eventually change the function to return void. Also the
driver core ignores the return value of mtk_disp_pwm_remove().

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Stable-dep-of: 36dd7f530ae7 ("pwm: mtk-disp: Disable shadow registers before setting backlight values")
Signed-off-by: Sasha Levin <sashal@kernel.org>