powerpc/usb: fix bug of CPU hang when missing USB PHY clock

when missing USB PHY clock, kernel booting up will hang during USB
initialization. We should check USBGP[PHY_CLK_VALID] bit to avoid
CPU hanging in this case.

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-fsl.h

@@ -61,4 +61,5 @@
 #define PLL_RESET               (1<<8)
 #define UTMI_PHY_EN             (1<<9)
 #define ULPI_PHY_CLK_SEL        (1<<10)
+#define PHY_CLK_VALID		(1<<17)
 #endif				/* _EHCI_FSL_H */