Add GPIO helper macros to the GPIO_STM32.h

[TeoMahnic]

Add helper macros for GPIO Pin mapping to the GPIO_STM32.h

Example:

// Pin mapping
#define GPIO_PORTA(n)   (  0U + (n))
#define GPIO_PORTB(n)   ( 16U + (n))
#define GPIO_PORTC(n)   ( 32U + (n))
#define GPIO_PORTD(n)   ( 48U + (n))
#define GPIO_PORTE(n)   ( 64U + (n))
#define GPIO_PORTF(n)   ( 80U + (n))
#define GPIO_PORTG(n)   ( 96U + (n))
#define GPIO_PORTH(n)   (112U + (n))
#define GPIO_PORTI(n)   (128U + (n))
#define GPIO_PORTJ(n)   (144U + (n))

[MiloradCvjetkovic]

Addressed in commit https://github.com/Open-CMSIS-Pack/CMSIS-Driver_STM32/commit/83f474beed902cb77b7458f4d23fdff08b90b4e1