Adding Flexcan driver support on Kernel

Adding Flexcan driver support on Kernel

On kernel menuconfig, add the following items:

[*] Networking support  --->
    <*>  CAN bus subsystem support  --->
        <*>  Raw CAN Protocol (raw access with CAN-ID filtering)
        <*>  Broadcast Manager CAN Protocol (with content filtering)
    CAN Device Drivers  --->
        <*> Virtual Local CAN Interface (vcan)
        [*] CAN devices debugging messages
        <*> Freescale FlexCAN