USB: ehci-omap: Improve PHY error handling

As the USB PHY layer never returns NULL we don't need
to check for that condition.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>