stm32/can: Fix clearing filters on CAN3 (bxCAN).

[projectgus]

Summary

This fix was split out from #15989.

The instance argument to HAL_CAN_ConfigFilter() is ignored for CAN1, CAN2 but needed for CAN3.

Testing

• Tested as part of stm32: Refactor pyb.CAN implementation, add tests. #15989.

[github-actions]

Code size report:

   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +4 +0.001% PYBV10
     mimxrt:    +0 +0.000% TEENSY40
        rp2:    +0 +0.000% RPI_PICO_W
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS
  qemu rv32:    +0 +0.000% VIRT_RV32