spinlock: Fix failing build for PREEMPT_RT

Since 1d71b30e1f85 ("sched.h: Move (spin|rwlock)_needbreak() to
spinlock.h") build fails for PREEMPT_RT, since there is no definition
available of either spin_needbreak() and rwlock_needbreak().

Since it was moved on the mentioned commit, it was placed inside a
!PREEMPT_RT part of the code, making it out of reach for an RT kernel.

Fix this by moving code it a few lines down so it can be reached by an
RT build, where it can also make use of the *_is_contended() definition
added by the spinlock_rt.h.

Fixes: d1d71b3 ("sched.h: Move (spin|rwlock)_needbreak() to
spinlock.h")
Signed-off-by: Leonardo Bras <leobras@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Acked-by: Waiman Long <longman@redhat.com>

Author: Leonardo Bras

include/linux/spinlock.h

@@ -449,6 +449,12 @@ static __always_inline int spin_is_contended(spinlock_t *lock)
 	return raw_spin_is_contended(&lock->rlock);
 }
 
+#define assert_spin_locked(lock)	assert_raw_spin_locked(&(lock)->rlock)
+
+#else  /* !CONFIG_PREEMPT_RT */
+# include <linux/spinlock_rt.h>
+#endif /* CONFIG_PREEMPT_RT */
+
 /*
  * Does a critical section need to be broken due to another
  * task waiting?: (technically does not depend on CONFIG_PREEMPTION,
@@ -480,12 +486,6 @@ static inline int rwlock_needbreak(rwlock_t *lock)
 #endif
 }
 
-#define assert_spin_locked(lock)	assert_raw_spin_locked(&(lock)->rlock)
-
-#else  /* !CONFIG_PREEMPT_RT */
-# include <linux/spinlock_rt.h>
-#endif /* CONFIG_PREEMPT_RT */
-
 /*
  * Pull the atomic_t declaration:
  * (asm-mips/atomic.h needs above definitions)