USB: host: ehci: introduce omap ehci-hcd driver

this driver has been sitting in linux-omap tree for quite
some time. It adds support for omap's ehci controller.

Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Vikram Pandita <vikram.pandita@ti.com>
Signed-off-by: Ajay Kumar Gupta <ajay.gupta@ti.com>
Signed-off-by: Anand Gadiyar <gadiyar@ti.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>