ov5640: Add /proc/driver/ov5640

Echo a register number to it to get a kernel message with the value:
	# echo 0x471d > /proc/driver/ov5640
	ov5640[471d] == 0x01

Use a second parameter to set a value. For example, this sets register
0x302c (drive strength) to 1x (value of 0):

	# echo 0x302c 0x00 > /proc/driver/ov5640

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>