speakup: fix uninitialized flush_lock

The flush_lock is uninitialized, use DEFINE_SPINLOCK
to define and initialize flush_lock.

Fixes: c6e3fd22 ("Staging: add speakup to the staging directory")
Reported-by: Hulk Robot <hulkci@huawei.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20201117012229.3395186-1-yangyingliang@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/accessibility/speakup/speakup_dectlk.c

@@ -37,7 +37,7 @@ static unsigned char get_index(struct spk_synth *synth);
 static int in_escape;
 static int is_flushing;
 
-static spinlock_t flush_lock;
+static DEFINE_SPINLOCK(flush_lock);
 static DECLARE_WAIT_QUEUE_HEAD(flush);
 
 static struct var_t vars[] = {