spi/txx9: Deletion of an unnecessary check before the function call "clk_disable"

The clk_disable() function tests whether its argument is NULL and then
returns immediately. Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-txx9.c

@@ -402,8 +402,7 @@ exit_busy:
 exit:
 	if (c->workqueue)
 		destroy_workqueue(c->workqueue);
-	if (c->clk)
-		clk_disable(c->clk);
+	clk_disable(c->clk);
 	spi_master_put(master);
 	return ret;
 }