USB: EHCI: ehci-mv: improve error handling in mv_ehci_enable()

mv_ehci_enable() did not disable and unprepare clocks in case of
failures of phy_init(). Besides, it did not take into account failures
of ehci_clock_enable() (in effect, failures of clk_prepare_enable()).
The patch fixes both issues and gets rid of redundant wrappers around
clk_prepare_enable() and clk_disable_unprepare() to simplify this a bit.

Found by Linux Driver Verification project (linuxtesting.org).
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Evgeny Novikov <novikov@ispras.ru>
Link: https://lore.kernel.org/r/20210708083056.21543-1-novikov@ispras.ruSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-mv.c

@@ -42,26 +42,25 @@ struct ehci_hcd_mv {
 	int (*set_vbus)(unsigned int vbus);
 };
 
-static void ehci_clock_enable(struct ehci_hcd_mv *ehci_mv)
+static int mv_ehci_enable(struct ehci_hcd_mv *ehci_mv)
 {
-	clk_prepare_enable(ehci_mv->clk);
-}
+	int retval;
 
-static void ehci_clock_disable(struct ehci_hcd_mv *ehci_mv)
-{
-	clk_disable_unprepare(ehci_mv->clk);
-}
+	retval = clk_prepare_enable(ehci_mv->clk);
+	if (retval)
+		return retval;
 
-static int mv_ehci_enable(struct ehci_hcd_mv *ehci_mv)
-{
-	ehci_clock_enable(ehci_mv);
-	return phy_init(ehci_mv->phy);
+	retval = phy_init(ehci_mv->phy);
+	if (retval)
+		clk_disable_unprepare(ehci_mv->clk);
+
+	return retval;
 }
 
 static void mv_ehci_disable(struct ehci_hcd_mv *ehci_mv)
 {
 	phy_exit(ehci_mv->phy);
-	ehci_clock_disable(ehci_mv);
+	clk_disable_unprepare(ehci_mv->clk);
 }
 
 static int mv_ehci_reset(struct usb_hcd *hcd)