usb:serial:pl2303: add GPIOs interface on PL2303

PL2303HX has two GPIOs, this patch add interface for it.

---
Changes v3-v4:
1: fix missing static for gpio_dir_mask and gpio_value_mask
2: reduce unneeded compile macro defined suggested by [email protected] 3: use true instead of 1 corrected by Linus Walleij
4: ignore return value of gpiochip_remove suggested by Linus Walleij 5: fix multi gpio_chips registered by pl2303 can't be distinguished in kernel space.

Give different labels to different gpio_chips is good for diagnostic, and we could identify per gpio_chip registered by pl2303 by try different lable name then detect its parent device.

 drivers/usb/serial/Kconfig  |  10 +++
 drivers/usb/serial/pl2303.c | 163 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 173 insertions(+)

index 3ce5c74..4bc0d0f 100644
@@ -516,6 +516,16 @@ config USB_SERIAL_PL2303
 	  To compile this driver as a module, choose M here: the
 	  module will be called pl2303.
 
+config USB_SERIAL_PL2303_GPIO
+	bool "USB Prolific 2303 Single Port GPIOs support"
+	depends on USB_SERIAL_PL2303 && GPIOLIB
+	---help---
+	  Say Y here if you want to use the GPIOs on PL2303 USB Serial single port
+	  adapter from Prolific.
+
+	  It support 2 GPIOs on PL2303HX currently,
+	  if unsure, say N.
+
 config USB_SERIAL_OTI6858
 	tristate "USB Ours Technology Inc. OTi-6858 USB To RS232 Bridge Controller"
 	help

1.8.5.5.dirty

This is OK with me now,

Yours,
Linus Walleij