x86/platform/intel-mid: Handle Intel Edison reboot correctly

When the Intel Edison module is powered with 3.3V, the reboot command makes
the module stuck.  If the module is powered at a greater voltage, like 4.4V
(as the Edison Mini Breakout board does), reboot works OK.

The official Intel Edison BSP sends the IPCMSG_COLD_RESET message to the
SCU by default. The IPCMSG_COLD_BOOT which is used by the upstream kernel
is only sent when explicitely selected on the kernel command line.

Use IPCMSG_COLD_RESET unconditionally which makes reboot work independent
of the power supply voltage.

[ tglx: Massaged changelog ]

Fixes: bda7b072

 ("x86/platform/intel-mid: Implement power off sequence")
Signed-off-by: Sebastian Panceac <sebastian@resin.io>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1519810849-15131-1-git-send-email-sebastian@resin.io