get_maintainer: exclude MAINTAINERS file(s) from --git-fallback

MAINTAINERS files generally have no specific maintainer but are updated by
individuals for subsystems all over the source tree.

Exclude MAINTAINERS file(s) from --git-fallback searches so the unlucky
individuals that update the files the most are not shown by default.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Link: https://lkml.kernel.org/r/2bacb0a9c06fbb6d56a43bf930e808c74243c908.camel@perches.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>