usb: common: ulpi: Constify static attribute_group struct

It is never modified, so make them const to allow the compiler to
put it in read-only memory. Done with the help of coccinelle.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20201125162500.37228-4-rikard.falkeborn@gmail.com


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