xen/spinlocks: spin_trylock with interrupts off is always fine

xen/spinlocks: spin_trylock with interrupts off is always fine

Even if a spinlock was taken with interrupts on before calling
spin_trylock() with interrupts off is fine, as it can't block.

Add a bool parameter "try" to check_lock() for handling this case.

Remove the call of check_lock() from _spin_is_locked(), as it really
serves no purpose and it can even lead to false crashes, e.g. when
a lock was taken correctly with interrupts enabled and the call of
_spin_is_locked() happened with interrupts off. In case the lock is
taken with wrong interrupt flags this will be catched when taking
the lock.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>