LU-12189 ec: code to add support for M to N parity

LU-12189 ec: code to add support for M to N parity

This code adds basic functionality for calculating N parities
for M data units. This allows much more than just working with
raid6 calculations. The code is derived from the Intel isa-l
userland library. Keep the code in an separate module for easy
merger upstream at a latter time.

Test-Parameters: trivial
Change-Id: Ie0bb5af2514c213db40de33139e03e16f9605ce8
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Adam Disney <disneyaw@ornl.gov>
Reviewed-on: https://review.whamcloud.com/47628
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>