accessiblity: speakup: Add missing misc_deregister in softsynth_probe

softsynth_probe misses a call misc_deregister() in an error path, this
patch fixes that.
Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Link: https://lore.kernel.org/r/20220511032937.2736738-1-zhengbin13@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/accessibility/speakup/speakup_soft.c

@@ -397,6 +397,7 @@ static int softsynth_probe(struct spk_synth *synth)
 	synthu_device.name = "softsynthu";
 	synthu_device.fops = &softsynthu_fops;
 	if (misc_register(&synthu_device)) {
+		misc_deregister(&synth_device);
 		pr_warn("Couldn't initialize miscdevice /dev/softsynthu.\n");
 		return -ENODEV;
 	}