[PATCH] pwm-backlight: fix probing from device-tree without enable-gpios

Since 257462dbf3ed ("pwm-backlight: switch to gpiod interface")
enable_gpio is no longer set and remains 0 when probing from
device-tree. This is a valid gpio number. With no enable-gpios
specified in the device-tree this is used and probing fails
with:

pwm-backlight lcd-backlight.3: failed to request GPIO#0: -16

Fix this by setting enable_gpio to -1 which is not a valid gpio
number.

Signed-off-by: Michael Olbrich <redacted>
---
 drivers/video/backlight/pwm_bl.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 38ca88b..5213d13 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c

@@ -211,6 +211,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 			dev_err(&pdev->dev, "failed to find platform data\n");
 			return ret;
 		}
+		devdata.enable_gpio = -1;
 
 		data = &defdata;
 	}

-- 
2.0.1