RDMA/rxe: Fix the problem "mutex_destroy missing"

When a mutex lock is not used any more, the function mutex_destroy
should be called to mark the mutex lock uninitialized.

Fixes: 8700e3e7

 ("Soft RoCE driver")
Signed-off-by: Yanjun.Zhu <yanjun.zhu@linux.dev>
Link: https://lore.kernel.org/r/20240314065140.27468-1-yanjun.zhu@linux.dev
Reviewed-by: Daisuke Matsuda <matsuda-daisuke@fujitsu.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>