regress fails on unknown mnemonic csrrw (#172)

I have regression fails, tried on riscv-perf-model and on my fork. 

Please check my work. I did not see any previous reference to this error
but I could have missed it.

MavisUnit.cpp was missing this file:
isa_file_path + "/isa_rv64zicsr.json",

these tests failed for me on regress
	  1 - olympia_json_test (Subprocess aborted)
	  2 - olympia_json_test_report_text (Subprocess aborted)
	  3 - olympia_json_test_report_text_direct (Subprocess aborted)
	  4 - olympia_json_test_report_html (Subprocess aborted)

...
Exception while running
Unknown mnemonic 'csrrw' in ExtractorDirectInfo
...
terminate called after throwing an instance of 'mavis::UnknownMnemonic'
  what():  Unknown mnemonic 'csrrw' in ExtractorDirectInfo
...

Co-authored-by: Jeff Nye <jeff@www.condorcomputing.com>