STM32 CAN : remove warning [-Wsign-compare]
STM32 CAN : remove warning [-Wsign-compare]

Detected with NUCLEO_G474RE build:
[Warning] stm32g4xx_hal_fdcan.h@1325,84: comparison is always true due to limited range of data type [-Wtype-limits]
[Warning] stm32g4xx_hal_fdcan.h@1331,46: comparison of integer expressions of different signedness: 'int' and 'unsigned int' [-Wsign-compare]
[Warning] stm32g4xx_hal_fdcan.h@1331,65: comparison of integer expressions of different signedness: 'int' and 'unsigned int' [-Wsign-compare]
[Warning] stm32g4xx_hal_fdcan.h@1325,61: comparison of integer expressions of different signedness: 'int' and 'unsigned int' [-Wsign-compare]
[Warning] stm32g4xx_hal_fdcan.h@1325,84: comparison of integer expressions of different signedness: 'int' and 'unsigned int' [-Wsign-compare]

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