tile: change lock initalization in hardwall

hardwall used __SPIN_LOCK_INITIALIZER directly instead of the preferred
__SPIN_LOCK_UNLOCKED. This also has the benefit that it will compile
when applying the preempt-rt patch series.

Signed-off-by: Henrik Austad <haustad@cisco.com>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>