devtools: fix file listing in maintainers check

devtools: fix file listing in maintainers check

When having multiple working trees, the main one has a .git directory
while attached trees have a .git file.
Thus the git check should work for both file and directory.

In the case there is no working tree (.git not readable), the command
"find" is used and should be able to list paths with wildcards.
Wildcards work only as shell expansion in the case of file paths,
so the quotes must be removed.

Fixes: 27c2ce563216 ("maintainers: start a Linux-style file")
Cc: stable@dpdk.org
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>