USB: ehci-omap: Fix autoloading of module

The module alias should be "ehci-omap" and not
"omap-ehci" to match the platform device name.
The omap-ehci module should now autoload correctly.

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