usb: host: oxu210hp: remove unused struct 'ehci_dbg_port'

usb: host: oxu210hp: remove unused struct 'ehci_dbg_port'

'ehci_dbg_port' is unused in oxu210hp-hcd.c since it's original
commit b92a78e582b1 ("usb host: Oxford OXU210HP HCD driver.")
when it was in a separate header.

Remove it.

Note, that this structure, and some others in the driver
are mostly clones of include/linux/usb/ehci_def.h.
Someone with the hardware to be able to test it might
be able to remove a lot more structs as well and just
use that header.

Signed-off-by: "Dr. David Alan Gilbert" <linux@treblig.org>
Link: https://lore.kernel.org/r/20240529210002.106369-1-linux@treblig.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>