usb: rearrange usb_ep_get()

usb: rearrange usb_ep_get()

There is no need to calculate the 'eps' variable in usb_ep_get()
if 'ep' is the control endpoint.  Instead the calculation should
be done after validating the input before returning an entry
indexed by the endpoint 'ep'.

Signed-off-by: Liam Merwick <liam.merwick@oracle.com>
Reviewed-by: Darren Kenny <Darren.Kenny@oracle.com>
Reviewed-by: Mark Kanda <Mark.Kanda@oracle.com>
Reviewed-by: Ameya More <ameya.more@oracle.com>
Message-id: 1549460216-25808-2-git-send-email-liam.merwick@oracle.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>