py/mphal.h contains declarations for generic mp_hal_XXX functions, such
as stdio and delay/ticks, which ports should provide definitions for. A
port will also provide mphalport.h with further HAL declarations.
Remove include of stm32f4xx_hal.h, replace by include of MICROPY_HAL_H
where needed, and make it compile without float support. This makes
these 3 modules much more generic and usable by other ports.
