Few issues related to stm32f723 (maybe others f7)

• it has a single precision FPU while modm builds with -mfpu=fpv5-d16 instead of -mfpu=fpv5-sp-d16
• the integrated USB HS phy seems not totally supported/initialized
• USB D+ and D- in USB HS are initialized with Gpio::OutputSpeed::High instead of Gpio::OutputSpeed::VeryHigh

I'll try to PR fixes soon.