get_maintainer: use filename-only regex match for Tegra

get_maintainer: use filename-only regex match for Tegra

Create a new N: entry type in MAINTAINERS which performs a regex match
against filenames; either those extracted from patch +++ or --- lines, or
those specified on the command-line using the -f option.

This provides the same benefits as using a K: regex option to match a set
of filenames (see commit eb90d08 "get_maintainer: allow keywords to match
filenames"), but without the disadvantage that "random" file content, such
as comments, will ever match the regex.  Hence, revert most of that
commit.

Switch the Tegra entry from using K: to N:

Reported-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>