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
picassowifi: defconfig: Update after enabling HRTICK

Change-Id: If6f9cfd3e989c3a0a278d32f1d441ec8e3f9ea60