Kinetis:SIM add paramiterized SIM_CLKDIVx_xxFRAC|DIV macros

  The makes for cleaner board definitions like:

   Divider output clock = Divider input clock * ((PLLFLLFRAC+1)/(PLLFLLDIV+1))
       SIM_CLKDIV3_FREQ = BOARD_SOPT2_FREQ × [ (PLLFLLFRAC+1) / (PLLFLLDIV+1)]
                 90 Mhz = 180 Mhz X [(0 + 1) / (1 + 1)]
    #define BOARD_SIM_CLKDIV3_PLLFLLFRAC  1
    #define BOARD_SIM_CLKDIV3_PLLFLLDIV   2
    #define BOARD_SIM_CLKDIV3_FREQ        (BOARD_SOPT2_FREQ * (BOARD_SIM_CLKDIV3_PLLFLLFRAC / BOARD_SIM_CLKDIV3_PLLFLLDIV))