STM32: Set valid filter number for CAN3
STM32: Set valid filter number for CAN3

Filter numbers 14 to 27 are reserved for dual CAN configuration.
However, CAN3 operates in single CAN configuration according to the
reference manual).

andcor02/mbed-os,CalSol/mbed,karsev/mbed-os,betzw/mbed-os,c1728p9/mbed-os,kjbracey-arm/mbed,Archcady/mbed-os,mazimkhan/mbed-os,andcor02/mbed-os,kjbracey-arm/mbed,karsev/mbed-os,ryankurte/mbed-os,andcor02/mbed-os,mazimkhan/mbed-os,c1728p9/mbed-os,CalSol/mbed,c1728p9/mbed-os,ryankurte/mbed-os,karsev/mbed-os,ryankurte/mbed-os,CalSol/mbed,CalSol/mbed,CalSol/mbed,mbedmicro/mbed,Archcady/mbed-os,ryankurte/mbed-os,mazimkhan/mbed-os,andcor02/mbed-os,Archcady/mbed-os,Archcady/mbed-os,betzw/mbed-os,betzw/mbed-os,Archcady/mbed-os,karsev/mbed-os,betzw/mbed-os,kjbracey-arm/mbed,ryankurte/mbed-os,andcor02/mbed-os,CalSol/mbed,c1728p9/mbed-os,kjbracey-arm/mbed,mazimkhan/mbed-os,betzw/mbed-os,andcor02/mbed-os,mbedmicro/mbed,mbedmicro/mbed,mbedmicro/mbed,c1728p9/mbed-os,karsev/mbed-os,mbedmicro/mbed,ryankurte/mbed-os,karsev/mbed-os,mazimkhan/mbed-os,betzw/mbed-os,mazimkhan/mbed-os,c1728p9/mbed-os,Archcady/mbed-os