drm/bridge: ti-sn65dsi86: Check for CONFIG_PWM using IS_REACHABLE()

Currently CONFIG_PWM is a bool but I intend to change it to tristate. If
CONFIG_PWM=m in the configuration, the cpp symbol CONFIG_PWM isn't
defined and so the PWM code paths in the ti-sn65dsi86 driver are not
used.

The correct way to check for CONFIG_PWM is using IS_REACHABLE which does
the right thing for all cases
CONFIG_DRM_TI_SN65DSI86 ∈ { y, m } x CONFIG_PWM ∈ { y, m, n }.

There is no change until CONFIG_PWM actually becomes tristate.

Signed-off-by: Uwe Kleine-König <[email protected]>
Reviewed-by: Louis Chauvet <[email protected]>
Reviewed-by: Robert Foss <[email protected]>
Reviewed-by: Douglas Anderson <[email protected]>
Signed-off-by: Douglas Anderson <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: ukleinek

drivers/gpu/drm/bridge/ti-sn65dsi86.c

@@ -195,7 +195,7 @@ struct ti_sn65dsi86 {
 	struct gpio_chip		gchip;
 	DECLARE_BITMAP(gchip_output, SN_NUM_GPIOS);
 #endif
-#if defined(CONFIG_PWM)
+#if IS_REACHABLE(CONFIG_PWM)
 	struct pwm_chip			*pchip;
 	bool				pwm_enabled;
 	atomic_t			pwm_pin_busy;
@@ -1362,7 +1362,7 @@ static struct auxiliary_driver ti_sn_bridge_driver = {
 /* -----------------------------------------------------------------------------
  * PWM Controller
  */
-#if defined(CONFIG_PWM)
+#if IS_REACHABLE(CONFIG_PWM)
 static int ti_sn_pwm_pin_request(struct ti_sn65dsi86 *pdata)
 {
 	return atomic_xchg(&pdata->pwm_pin_busy, 1) ? -EBUSY : 0;
@@ -1956,7 +1956,7 @@ static int ti_sn65dsi86_probe(struct i2c_client *client)
 			return ret;
 	}
 
-	if (IS_ENABLED(CONFIG_PWM)) {
+	if (IS_REACHABLE(CONFIG_PWM)) {
 		ret = ti_sn65dsi86_add_aux_device(pdata, &pdata->pwm_aux, "pwm");
 		if (ret)
 			return ret;