mdss: dsi: replace deprecated pwm_config_us with pwm_config

Replace deprecated PWM API pwm_config_us with pwm_config to avoid
failures while setting backlight to 0.

Change-Id: I3ab9d12572578a225cf842960d08c496891e2f13
Signed-off-by: Vishnuvardhan Prodduturi <vproddut@codeaurora.org>
diff --git a/drivers/video/fbdev/msm/mdss_dsi_panel.c b/drivers/video/fbdev/msm/mdss_dsi_panel.c
index d84cf5e..1cbaa44 100644
--- a/drivers/video/fbdev/msm/mdss_dsi_panel.c
+++ b/drivers/video/fbdev/msm/mdss_dsi_panel.c
@@ -79,10 +79,10 @@
 
 	if (level == 0) {
 		if (ctrl->pwm_enabled) {
-			ret = pwm_config_us(ctrl->pwm_bl, level,
-					ctrl->pwm_period);
+			ret = pwm_config(ctrl->pwm_bl, 0,
+					ctrl->pwm_period * NSEC_PER_USEC);
 			if (ret)
-				pr_err("%s: pwm_config_us() failed err=%d.\n",
+				pr_err("%s: pwm_config() failed err=%d.\n",
 						__func__, ret);
 			pwm_disable(ctrl->pwm_bl);
 		}