[GFS2] Update git tree name/location

The plan is to have two trees. One for bug fixes to be sent on a
regular basis (-fixes) and another called -nmw which will contain items
queued for the next merge window (hence the name). The -nmw tree
will come & go according to need.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --cc MAINTAINERS
Simple merge