fsl/usb: Resolve PHY_CLK_VLD instability issue for ULPI phy

For controller versions greater than 1.6, setting ULPI_PHY_CLK_SEL
bit when USB_EN bit is already set causes instability issues with
PHY_CLK_VLD bit. So USB_EN is set only for IP controller version
below 1.6 before setting ULPI_PHY_CLK_SEL bit

Signed-off-by: Ramneek Mehresh <ramneek.mehresh@freescale.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>