boards: stm32: Move USB pins to device tree configuration

Move STM32 based board USB pin configuration to device tree.

Exceptions:
* olimex_stm32_h407: Node not enabled and not documented.
Signal added in disabled node.
* L0/G4 based boards as signals are not available yet.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>