arm: Kconfig: Add SCHED_HRTICK

The arm platform has opted to ignore the mainline Kconfig.hz
and add their own definition here instead.

Add this missing config item.

Change-Id: I034978b79c05ce7a237b8f50217ceb2fe076ffc2
mondrianwifi: defconfig: Update CONFIG_SCHED config

Change-Id: Id55a00ed62a4f785d4aef91c335344ca31521f02