[ARM] pxa/pcm990: use negative number for an invalid GPIO in camera data

0 is a valid GPIO number, use a negative number to specify, that this camera
doesn't have a GPIO for bus-width switching.

Signed-off-by: Guennadi Liakhovetski <[e-mail]>
Signed-off-by: Eric Miao <[e-mail]>

arch/arm/mach-pxa/pcm990-baseboard.c

···
 		.gpio	= NR_BUILTIN_GPIO + 1,
 	}, {
 		.bus_id	= 0, /* Must match with the camera ID above */
+		.gpio	= -ENXIO,
 	}
 };