[HAL][GPIO] Fix documentation errors.

[schilkp]

Hi!

This fixes some trivial typos in GPIO function doxygen comments. Most notably some comments specified that:

 This parameter can be any combination of GPIO_Pin_x where x can be (0..15).

While the actual macros are:

#define GPIO_PIN_0                 ((uint16_t)0x0001)  /* Pin 0 selected    */
#define GPIO_PIN_1                 ((uint16_t)0x0002)  /* Pin 1 selected    */
...

This caused some confusion for students in a course I help run.

Please note that this exact typo is found in many places across most other HAL driver repos. Some examples:

• https://github.com/STMicroelectronics/stm32g0xx_hal_driver/blob/48c6ac475eee0a958f611b2e9305fe25b95fc9bc/Src/stm32g0xx_hal_gpio.c#L286
• https://github.com/STMicroelectronics/stm32l4xx_hal_driver/blob/cbc2a703ba03114fe83e1fc1273671081ecd785e/Src/stm32l4xx_hal_gpio.c#L390
• https://github.com/STMicroelectronics/stm32l1xx_hal_driver/blob/36266520b04570310d3dcc343d1c479b2c2bbbae/Src/stm32l1xx_hal_gpio.c#L466
• https://github.com/STMicroelectronics/stm32l0xx_hal_driver/blob/9d7402ea840357d8224592af199a132c3340ee1f/Src/stm32l0xx_hal_gpio.c#L450
• https://github.com/STMicroelectronics/stm32g4xx_hal_driver/blob/7c2e19ec21714f0d993ae5bfe8859a45debcfdd6/Src/stm32g4xx_hal_gpio.c#L452
• https://github.com/STMicroelectronics/stm32f7xx_hal_driver/blob/343e421f8ac1018481aef751e4de913f1080d5b0/Src/stm32f7xx_hal_gpio.c#L367
• https://github.com/STMicroelectronics/stm32f3xx_hal_driver/blob/d2a8fb62d4de6fbad2f575c68386401184e771e0/Src/stm32f3xx_hal_gpio.c#L461
• https://github.com/STMicroelectronics/stm32f1xx_hal_driver/blob/3f810594a401e7b17771e6ad1d7c86bdfbb45cb0/Src/stm32f1xx_hal_gpio.c#L508

....

Thanks!

[TOUNSTM]

ST Internal Reference: 168718