drivers/video/backlight/l4f00242t03.c: make 1-bit signed field unsigned

Fixes sparse warning:
drivers/video/backlight/l4f00242t03.c:28:21: error: dubious one-bit signed bitfield
Signed-off-by: Mariusz Kozlowski <mk@lab.zgora.pl>
Acked-by: Richard Purdie <rpurdie@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/video/backlight/l4f00242t03.c

@@ -25,7 +25,7 @@
 struct l4f00242t03_priv {
 	struct spi_device	*spi;
 	struct lcd_device	*ld;
-	int lcd_on:1;
+	unsigned int lcd_on:1;
 	struct regulator *io_reg;
 	struct regulator *core_reg;
 };