extcon: Use the unique id for external connector instead of string

This patch uses the unique id to identify the type of external connector instead
of string name. The string name have the many potential issues. So, this patch
defines the 'extcon' enumeration which includes all supported external connector
on EXTCON subsystem. If new external connector is necessary, the unique id of
new connector have to be added in 'extcon' enumeration. There are current
supported external connector in 'enum extcon' as following:

enum extcon {
	EXTCON_NONE		= 0x0,

	/* USB external connector */
	EXTCON_USB		= 0x1,
	EXTCON_USB_HOST		= 0x2,

	/* Charger external connector */
	EXTCON_TA		= 0x10,
	EXTCON_FAST_CHARGER	= 0x11,
	EXTCON_SLOW_CHARGER	= 0x12,
	EXTCON_CHARGE_DOWNSTREAM = 0x13,

	/* Audio and video external connector */
	EXTCON_LINE_IN		= 0x20,
	EXTCON_LINE_OUT		= 0x21,
	EXTCON_MICROPHONE	= 0x22,
	EXTCON_HEADPHONE	= 0x23,

	EXTCON_HDMI		= 0x30,
	EXTCON_MHL		= 0x31,
	EXTCON_DVI		= 0x32,
	EXTCON_VGA		= 0x33,
	EXTCON_SPDIF_IN		= 0x34,
	EXTCON_SPDIF_OUT	= 0x35,
	EXTCON_VIDEO_IN		= 0x36,
	EXTCON_VIDEO_OUT	= 0x37,

	/* Miscellaneous external connector */
	EXTCON_DOCK		= 0x50,
	EXTCON_JIG		= 0x51,
	EXTCON_MECHANICAL	= 0x52,

	EXTCON_END,
};

For example in extcon-arizona.c:
To use unique id removes the potential issue about handling
the inconsistent name of external connector with string.
- Previously, use the string to register the type of arizona jack connector
static const char *arizona_cable[] = {
	"Mechanical",
	"Microphone",
	"Headphone",
	"Line-out",
};
- Newly, use the unique id to register the type of arizona jack connector
static const enum extcon arizona_cable[] = {
	EXTCON_MECHANICAL,
	EXTCON_MICROPHONE,
	EXTCON_HEADPHONE,
	EXTCON_LINE_OUT,

	EXTCON_NONE,
};

And this patch modify the prototype of extcon_{get|set}_cable_state_() which
uses the 'enum extcon id' instead of 'cable_index'. Because although one more
extcon drivers support USB cable, each extcon driver might has the differnt
'cable_index' for USB cable. All extcon drivers can use the unique id number
for same external connector with modified extcon_{get|set}_cable_state_().

- Previously, use 'cable_index' on these functions:
extcon_get_cable_state_(struct extcon_dev*, int cable_index)
extcon_set_cable_state_(struct extcon_dev*, int cable_index, bool state)

-Newly, use 'enum extcon id' on these functions:
extcon_get_cable_state_(struct extcon_dev*, enum extcon id)
extcon_set_cable_state_(struct extcon_dev*, enum extcon id, bool state)

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Felipe Balbi <balbi@ti.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Roger Quadros <rogerq@ti.com>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Acked-by: Ramakrishna Pallala <ramakrishna.pallala@intel.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
[arnd: Report the build break about drivers/usb/phy/phy-tahvo.c after using the
unique id for external connector insteadf of string]
Reported-by: Arnd Bergmann <arnd@arndb.de>
[dan.carpenter: Report the build warning of extcon_{set|get}_cable_state_()]
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>