M7 dcache ctrl via a parameter (#11769)

* Support for armv7-m_dcache control via parameter

  The FORCE_F7_DCACHE parameter can be set to
   0 - (default) if Eratta exits turn dcache off else leave it on
   1 -  Force it off
   2 -  Force it on

   At boot the system will disable the d-cache if the silicon
   has the 1259864 Data corruption in a sequence of Write-Through
   stores and loads eratta.

   Post nsh script execution the FORCE_F7_DCACHE paramater
   will be used to set the d-cache to the state indicated
   above.