spi: spi-txx9: Add missing clock (un)prepare calls for CCF

While the custom minimal TXx9 clock implementation doesn't need or use
clock (un)prepare calls (they are dummies if !CONFIG_HAVE_CLK_PREPARE),
they are mandatory when using the Common Clock Framework.

Hence add them, to prepare for the advent of CCF.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

drivers/spi/spi-txx9.c

···
 		c->clk = NULL;
 		goto exit;
 	}
-	ret = clk_enable(c->clk);
+	ret = clk_prepare_enable(c->clk);
 	if (ret) {
 		c->clk = NULL;
 		goto exit;
···
 exit_busy:
 	ret = -EBUSY;
 exit:
-	clk_disable(c->clk);
+	clk_disable_unprepare(c->clk);
 	spi_master_put(master);
 	return ret;
 }
···
 	struct txx9spi *c = spi_master_get_devdata(master);
 
 	flush_work(&c->work);
-	clk_disable(c->clk);
+	clk_disable_unprepare(c->clk);
 	return 0;
 }