power/reset: xgene-reset: Fix prototype of xgene_restart()

The xgene-reset driver uses xgene_restart() as arm_pm_restart() but that
function should take an enum reset_type as the first argument rather than
a char. Fix this; the paramter is not referenced in the implementation.

Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Sebastian Reichel <sre@kernel.org>