NUCLEO_F207ZG extending PeripheralPins.c: all available alternate functions can be used now

Through some minor extensions it is now possible to use all available alternate functions of a specific gpio pin. These alternatives exist up to now only as commented lines in PeripheralPins.c.
An API change is not necessary for this new functionality, only several pin definitions.

The new definitions now looks like:

    {PA_0,            ADC_1, STM_PIN_DATA_EXT(STM_MODE_ANALOG, GPIO_NOPULL, 0, 0, 0)},  // ADC1_IN0
    {PA_0_ALT0,  ADC_2, STM_PIN_DATA_EXT(STM_MODE_ANALOG, GPIO_NOPULL, 0, 0, 0)},  // ADC2_IN0 // choice: PA_0 with ADC_1
    {PA_0_ALT1,  ADC_3, STM_PIN_DATA_EXT(STM_MODE_ANALOG, GPIO_NOPULL, 0, 0, 0)},  // ADC3_IN0 // choice: PA_0 with ADC_1

PA_0, PA_0_ALT0 or PA_0_ALT1 has to be used as pin names for the usage of the three possible ADC blocks (ADC1, ADC2, ADC3) connected to the pin (PA_0).

Author: ohagendorf