MIPI CSI: Add board validation option.

Add the IO_BOARD_VALIDATION option to the MIPI_CSI_OPION build options.

This option generates PWM signals on the MIPI CSI interface to check
board connectivity. The PWM signals have a different increasing duty
cycle from data to clock to control signasls on the interface.

Please note this requires manual Verilog source code changes to CorePWM.
file: components/Actel/DirectCore/corepwm/4.5.100/rtl/vlog/core/reg_if.v
Lines 99 and 100 nedd to  be changed as follows:
  from:
         psh_enable_reg1  <= 0;
         psh_enable_reg2  <= 0;

  to:
         psh_enable_reg1  <= 8'b11111111;
         psh_enable_reg2  <= 8'b11111111;