LU-12678 lnet: discard LNET_MD_PHYS

LU-12678 lnet: discard LNET_MD_PHYS

This macro has no value and is never set.
It claims "compatibility with Cray Portals", yet cray-dvs
   git://github.com/glennklockwood/cray-dvs.git
does not use it in any non-trivial way.

Much has changed in lnet and lib-md since 2007 when this
value was added - it seems likely that this really
is dead.

So remove it.  If/when this results in problems, it can
easily be re-added and more details can be provided at
that time.

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: Idef9389f4c0993adbdf088d0ccd9a0dc1449e86e
Reviewed-on: https://review.whamcloud.com/39301
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Alexey Lyashkov <alexey.lyashkov@hpe.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>