staging: lustre: ptlrpc: Move NRS structures out of lustre_net.h

NRS specific structures are not needed in the rest of the PtlRPC code.
It is more appropriate for these structures to be defined in a
separate header. This commit creates a lustre_nrs.h header for the
generic NRS structures, and policy-specific headers for the various
NRS policies.

Signed-off-by: Chris Horn <hornc@cray.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-2667
Reviewed-on: http://review.whamcloud.com/13966


Reviewed-by: Henri Doreau <henri.doreau@cea.fr>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>