powerpc/83xx: Add shutdown request support to MCU handling on MPC8349 MITX

This patch add support for calling ctrl_alt_del() when the power button is
pressed for more than about 2 seconds on some freescale MPC83xx evaluation
boards and reference design.

The code uses a kthread to poll the CTRL_BTN bit each second.

Also change Kconfig entry of the driver to bool, as device's gpio
registration is broken when loading as module.

Tested on an MPC8315E RDB board.

Signed-off-by: Fabio Baltieri <fabio.baltieri@gmail.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index 9fdb9b6..e458872 100644
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -346,7 +346,7 @@
 	  on-board peripherals.
 
 config MCU_MPC8349EMITX
-	tristate "MPC8349E-mITX MCU driver"
+	bool "MPC8349E-mITX MCU driver"
 	depends on I2C && PPC_83xx
 	select GENERIC_GPIO
 	select ARCH_REQUIRE_GPIOLIB