[RISC-V] Revert CMO patch from Oct

[Jeff Law]

I've had a TODO for a while to remove the CMO patch from October; 
essentially the C API docs for this stuff aren't approved yet.  Until 
that MR gets merged we should not expose this API.


Specifically I'm reverting:
   Revert "[PATCH 1/2] RISC-V:Add intrinsic support for the CMOs extensions"
    
    This reverts commit d2c8548e0ce51dac6bc51d37236c50f98fca82f0.

   Revert "[PATCH 2/2] RISC-V:Add intrinsic cases for the CMOs extensions"
    
    This reverts commit b22d9c8f8216d15773dee4f9677c6b26aff507fd.


Jeff