stm32cube: add missing include guards for stm32g0xx_hal_hcd.h

The content of stm32g0xx_hal_hcd.h should be included only
on devices where the usb peripheral is available,
but this is not the case in STM32CubeG0 v1.4.0 release.
This commit fixes that issue.

Signed-off-by: Thomas Stranger <thomas.stranger@outlook.com>