usb: gadget: Drop usb_gadget_controller_number()

usb: gadget: Drop usb_gadget_controller_number()

The bcdDevice field is defined as
|Device release number in binary-coded decimal
in the USB 2.0 specification. We use this field to distinguish the UDCs
from each other. In theory this could be used on the host side to apply
certain quirks if the "special" UDC in combination with this gadget is
used. This hasn't been done as far as I am aware. In practice it would
be better to fix the UDC driver before shipping since a later release
might not need this quirk anymore.

This patch removes the newly unused function. Linux stopped using this
functionality in 2012, remove it from U-Boot as well.

Matching Linux kernel commit:
ed9cbda63d45 ("usb: gadget: remove usb_gadget_controller_number()")

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Tested-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Tested-by: Mattijs Korpershoek <mkorpershoek@baylibre.com> # on vim3
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Link: https://lore.kernel.org/r/20240609213449.194762-3-marek.vasut+renesas@mailbox.org
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>