media: i2c: imx290: Fix number of controls in v4l2_ctrl_handler_init

The number is only a hint, but may as well be correct.

Fixes: 471e0029 ("media: i2c: imx290: Convert HMAX setting into V4L2_CID_HBLANK")
Fixes: be0b9b7a ("media: i2c: imx290: Add support for V4L2_CID_VBLANK")
Fixes: 8483f0d7 ("media: i2c: imx290: Add exposure control to the driver.")
Fixes: 9764f345 ("media: i2c: imx290: Add H and V flip controls")
Signed-off-by: David Plowman <david.plowman@raspberrypi.com>