ahci: imx: fix the build warning

Add the default as the last entry to fix the following
build warning introduced by commit.
e5878732 ("ahci: imx: add the imx6qp ahci sata support")

drivers/ata/ahci_imx.c: In function 'imx_sata_disable':
drivers/ata/ahci_imx.c:478:2: warning: enumeration value 'AHCI_IMX53'
not handled in switch [-Wswitch]
  switch (imxpriv->type) {
	    ^~~~~~
Signed-off-by: NRichard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

drivers/ata/ahci_imx.c

@@ -490,6 +490,9 @@ static void imx_sata_disable(struct ahci_host_priv *hpriv)
 				   IMX6Q_GPR13_SATA_MPLL_CLK_EN,
 				   !IMX6Q_GPR13_SATA_MPLL_CLK_EN);
 		break;
+
+	default:
+		break;
 	}
 
 	clk_disable_unprepare(imxpriv->sata_ref_clk);