mpc83xx: restrict UTMI PHY configuration to 831x parts

mpc83xx: restrict UTMI PHY configuration to 831x parts

i.e, to those parts that have PHY_CLK_VALID bits in their USB
CONTROL registers:

mpc8308	 WU_INT, PHY_CLK_SEL, USB_EN, WU_INT_EN, ULPI_INT_EN
mpc831x	 PHY_CLK_VALID, WU_INT, CLKIN_SEL, PHY_CLK_SEL, UTMI_PHY_EN,
	 PLL_RESET, REFSEL, OTG_PORT, KEEP_OTG_ON, LSF_EN, USB_EN,
	 ULPI_INT_EN
mpc834x	 USB_EN, ULPI_INT1_EN (MPH only), ULPI_INT0_EN
mpc837x	 USB_EN, ULPI_INT_EN

(mpc832x, mpc8360 don't have a USB_EHCI_FSL compatible controller)

this prevents non-831x parts from never completing cpu_init_f(),
because the (non-existent) PHY_CLK_VALID bit never gets set.

Reported-by: Andre Schwarz <andre.schwarz@matrix-vision.de>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Tested-by: Andre Schwarz <andre.schwarz@matrix-vision.de>