locking: Make rwsem_assert_held_write_nolockdep() build with PREEMPT_RT=y

The commit cited below broke the build for PREEMPT_RT because
rwsem_assert_held_write_nolockdep() passes a struct rw_semaphore but
rw_base_assert_held_write() expects struct rwbase_rt. Fixing the type alone
leads to the problem that WARN_ON() is not found because bug.h is missing.

In order to resolve this:

 - Keep the assert (WARN_ON()) in rwsem.h (not rwbase_rt.h)

 - Make rwsem_assert_held_write_nolockdep() do the implementation
   specific (rw_base) writer check.

 - Replace the "inline" with __always_inline which was used before.

Fixes: f70405af

 ("locking: Add rwsem_assert_held() and rwsem_assert_held_write()")
Reported-by: Clark Williams <williams@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20240319182050.U4AzUF3I@linutronix.de