mfd: omap-usb-host: Mark expected switch fall-throughs

Mark switch cases where we are expecting to fall through.

This patch fixes the following warnings:

drivers/mfd/omap-usb-host.c: In function 'usbhs_runtime_resume':
drivers/mfd/omap-usb-host.c:303:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
    if (!IS_ERR(omap->hsic480m_clk[i])) {
       ^
drivers/mfd/omap-usb-host.c:313:3: note: here
   case OMAP_EHCI_PORT_MODE_TLL:
   ^~~~
drivers/mfd/omap-usb-host.c: In function 'usbhs_runtime_suspend':
drivers/mfd/omap-usb-host.c:345:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
    if (!IS_ERR(omap->hsic480m_clk[i]))
       ^
drivers/mfd/omap-usb-host.c:349:3: note: here
   case OMAP_EHCI_PORT_MODE_TLL:
   ^~~~
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

drivers/mfd/omap-usb-host.c

@@ -308,7 +308,7 @@ static int usbhs_runtime_resume(struct device *dev)
 					 i, r);
 				}
 			}
-		/* Fall through as HSIC mode needs utmi_clk */
+		/* Fall through - as HSIC mode needs utmi_clk */
 
 		case OMAP_EHCI_PORT_MODE_TLL:
 			if (!IS_ERR(omap->utmi_clk[i])) {
@@ -344,7 +344,7 @@ static int usbhs_runtime_suspend(struct device *dev)
 
 			if (!IS_ERR(omap->hsic480m_clk[i]))
 				clk_disable_unprepare(omap->hsic480m_clk[i]);
-		/* Fall through as utmi_clks were used in HSIC mode */
+		/* Fall through - as utmi_clks were used in HSIC mode */
 
 		case OMAP_EHCI_PORT_MODE_TLL:
 			if (!IS_ERR(omap->utmi_clk[i]))