usb: gadget: Complete fsl qe/udc driver conversion

commit ec39e2ae (usb: gadget: Update fsl_qe_udc to use
usb_endpoint_descriptor inside the struct usb_ep) did
not completely convert the fsl gadget drivers to use
the desc in usb_ep as described in commit messages.

Fix the macros that were still referencing the old
pointer.

Signed-off-by: Ben Collins <bcollins@ubuntu.com>
Cc: Ido Shayevitz <idos@codeaurora.org>
[ balbi@ti.com : brush up commit log a bit ]

Signed-off-by: Felipe Balbi <balbi@ti.com>