USB: serial: ftdi_sio: clean up chip type enum

Clean up the chip type enum by dropping the explicit values and moving
the definition to the implementation to make it easier to add further
types.

Signed-off-by: Johan Hovold <[e-mail]>

drivers/usb/serial/ftdi_sio.c

···
 #define DRIVER_AUTHOR "Greg Kroah-Hartman <[e-mail]>, Bill Ryder <[e-mail]>, Kuba Ober <[e-mail]>, Andreas Mohr, Johan Hovold <[e-mail]>"
 #define DRIVER_DESC "USB FTDI Serial Converters Driver"
 
+enum ftdi_chip_type {
+	SIO,
+	FT8U232AM,
+	FT232BM,
+	FT2232C,
+	FT232RL,
+	FT2232H,
+	FT4232H,
+	FT232H,
+	FTX,
+};
 
 struct ftdi_private {
 	enum ftdi_chip_type chip_type;

drivers/usb/serial/ftdi_sio.h

···
  * not supported by the FT8U232AM).
  */
 
-enum ftdi_chip_type {
-	SIO = 1,
-	FT8U232AM = 2,
-	FT232BM = 3,
-	FT2232C = 4,
-	FT232RL = 5,
-	FT2232H = 6,
-	FT4232H = 7,
-	FT232H  = 8,
-	FTX     = 9,
-};
-
 enum ftdi_sio_baudrate {
 	ftdi_sio_b300 = 0,
 	ftdi_sio_b600 = 1,