locking/rtmutex: switch to EXPORT_SYMBOL() for ww_mutex_lock{,_interruptible}()

We can use EXPORT_SYMBOL() instead of EXPORT_SYMBOL_GPL() in
ww_mutex_lock_interruptible() and ww_mutex_lock(). That match
ww_mutex_unlock() well. And also good for 3rd kernel modules.

Link: https://lore.kernel.org/r/20220803062430.1307312-1-yajun.deng@linux.dev


Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>