microblaze: Switch to standard restart handler

The microblaze uses the legacy APIs to dig out a GPIO pin
defined in the root of the device tree to issue a hard
reset of the platform.

Asserting a hard reset should be done using the standard
DT-enabled and fully GPIO descriptor aware driver in
drivers/power/reset/gpio-restart.c using the bindings
from Documentation/devicetree/bindings/power/reset/gpio-restart.txt

To achieve this, first make sure microblaze makes use of
the standard kernel restart path utilizing do_kernel_restart()
from <linux/reboot.h>. Put in some grace time and an
emergency print if the restart does not properly assert.

As this is basic platform functionality we patch the DTS
file and defconfig in one go for a lockstep change.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
ChangeLog v1->v2:
- Fix the reset GPIOs property in the DTS file to be
  just "gpios" as expected by the driver.

Hi Michal, would be great if you could test and fix this up
so I can get rid of one more site where legacy GPIO is used.
I am unsure of the appropriate polarity and delays, hence the
comments in the DTS file.
6 files changed