For the most part, the gate lock is nested with a wait queue hard lock
- which requires hard irqs to be off - to access the protected
sections. Therefore we would not benefit in the common case from the
preemption disabling feature we are going to add to the EVL-specific
spinlock. Make it a hard lock to clarify the intent.

Signed-off-by: Philippe Gerum <rpm@xenomai.org>