intel-vbtn: new driver for Intel Virtual Button

This driver supports power button event in Intel Virtual Button currently.
New Dell XPS 13 requires this driver for the power button.

This driver is copied/modified from intel-hid.c
Most credit goes to the author of intel-hid.c,
Alex Hung <alex.hung@canonical.com>

Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>

drivers/platform/x86/Kconfig

@@ -774,6 +774,18 @@ config INTEL_HID_EVENT
 	  To compile this driver as a module, choose M here: the module will
 	  be called intel_hid.
 
+config INTEL_VBTN
+	tristate "INTEL VIRTUAL BUTTON"
+	depends on ACPI
+	depends on INPUT
+	select INPUT_SPARSEKMAP
+	help
+	  This driver provides support for the Intel Virtual Button interface.
+	  Some laptops require this driver for power button support.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called intel_vbtn.
+
 config INTEL_SCU_IPC
 	bool "Intel SCU IPC Support"
 	depends on X86_INTEL_MID