media: ov2740: change the minimal exposure value to 4

The minimal valid exposure value should be 4 lines instead of 8 for
ov2740 mannual exposure control.

Signed-off-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/i2c/ov2740.c

@@ -37,7 +37,7 @@
 
 /* Exposure controls from sensor */
 #define OV2740_REG_EXPOSURE		0x3500
-#define OV2740_EXPOSURE_MIN		8
+#define OV2740_EXPOSURE_MIN		4
 #define OV2740_EXPOSURE_MAX_MARGIN	8
 #define OV2740_EXPOSURE_STEP		1