AP_HAL_ChibiOS: Correct the README.md for fmuv5 boards

the IST8310 magnetometer uses I2C, not SPI

libraries/AP_HAL_ChibiOS/hwdef/CUAVv5/README.md

@@ -12,7 +12,7 @@ The full schematics of the board are available here:
  - Three IMUs: ICM20689, MPU6000 and BMI055
  - internal vibration isolation for IMUs
  - MS5611 SPI barometer
- - builtin SPI IST8310 magnetometer
+ - builtin I2C IST8310 magnetometer
  - microSD card slot
  - 6 UARTs plus USB
  - 14 PWM outputs

libraries/AP_HAL_ChibiOS/hwdef/PH4-mini/README.md

@@ -7,7 +7,7 @@ The Pixhawk4-Mini flight controller is sold by [Holybro](http://www.holybro.com/
  - STM32F765 microcontroller
  - Two IMUs: ICM20689 and BMI055
  - MS5611 SPI barometer
- - builtin SPI IST8310 magnetometer
+ - builtin I2C IST8310 magnetometer
  - microSD card slot
  - 5 UARTs plus USB
  - 8 PWM outputs

libraries/AP_HAL_ChibiOS/hwdef/Pixhawk4/README.md

@@ -7,7 +7,7 @@ The Pixhawk4 flight controller is sold by [Holybro](http://www.holybro.com/produ
  - STM32F765 microcontroller
  - Two IMUs: ICM20689 and BMI055
  - MS5611 SPI barometer
- - builtin SPI IST8310 magnetometer
+ - builtin I2C IST8310 magnetometer
  - microSD card slot
  - 6 UARTs plus USB
  - 14 PWM outputs