usb: kbd: implement special keys

Provide support for F1-F12, Insert, Delete, Home, End, Page Up, Page Down.

As this leads to a size increase provide a customizing setting
CONFIG_USB_KEYBOARD_FN_KEYS.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/drivers/usb/Kconfig b/drivers/usb/Kconfig
index 9af78e8..bea4a92 100644
--- a/drivers/usb/Kconfig
+++ b/drivers/usb/Kconfig
@@ -100,6 +100,12 @@
 
 if USB_KEYBOARD
 
+config USB_KEYBOARD_FN_KEYS
+	bool "USB keyboard function key support"
+	help
+	  Say Y here if you want support for keys F1 - F12, INS, HOME, DELETE,
+	  END, PAGE UP, and PAGE DOWN.
+
 choice
 	prompt "USB keyboard polling"
 	default SYS_USB_EVENT_POLL