usb: gadget: tegra-xudc: Constify static structs

Constify a couple of ops-structs that are never modified, to let the
compiler put them in read-only memory.

Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20210513200908.448351-1-rikard.falkeborn@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>