layerscape: fix compile issue for usb ehci-fsl driver

When build firmware for layerscape target with CONFIG_ALL_NONSHARED=y,
there would be a compile issue of usb ehci-fsl driver. Actually this
driver was for PPC platforms initially and was not ready for non-PPC
now, but a kernel kconfig patch removed PPC dependency for it. So that
kernel patch should be reverted.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>