test_tickless: Change test_tickless location to tests/kernel/test_tickless/

Tickless test dependency on legacy API is resolved, Changing
test directory from tests/legacy/kernel/test_tickless to
tests/kernel/test_tickless/.

Jira: ZEP-2008

Signed-off-by: Youvedeep Singh <youvedeep.singh@intel.com>
Change-Id: I0b53ae6eff3a915d988d3234592eb5f8b425b371