extcon: add Maxim MAX3355 driver

Maxim Integrated MAX3355E chip integrates a charge pump and comparators to
enable a system with an integrated USB OTG dual-role transceiver to
function as an USB OTG dual-role device. In addition to sensing/controlling
Vbus, the chip also passes thru the ID signal from the USB OTG connector.
On some Renesas boards, this signal is just fed into the SoC thru a GPIO
pin -- there's no real OTG controller, only host and gadget USB controllers
sharing the same USB bus; however, we'd like to allow host or gadget
drivers to be loaded depending on the cable type, hence the need for the
MAX3355 extcon driver. The Vbus status signals are also wired to GPIOs
(however, we aren't currently interested in them), the OFFVBUS# signal is
controlled by the host controllers, there's also the SHDN# signal wired to
a GPIO, it should be driven high for the normal operation.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Rob Herring <robh@kernel.org>
[cw00.choi: Add the GPIOLIB dependency]
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>