api: Reorder API calls by version

Reorder the functions in nccl_ofi_api.cpp so that the functions are all
grouped by API type (ie, all the sends are together) and then ordered
by API version.  This is to simplify a follow-on commit that changes
API functions to always be versioned.

Signed-off-by: Brian Barrett <[email protected]>

Author: bwbarrett