get_maintainer.pl: find maintainers for removed files

For removed files, get_maintainer.pl doesn't find any maintainers (besides
the default linux-kernel@vger.kernel.org), as it only looks at the "+++"
lines, which are "/dev/null" for removals.  Fix this by extending the
parsing to the "---" lines.

E.g. for the two line test patch below the real score maintainers will now
be found:

    --- a/arch/score/include/asm/dma-mapping.h
    +++ /dev/null
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/get_maintainer.pl

@@ -433,7 +433,7 @@ foreach my $file (@ARGV) {
 
 	while (<$patch>) {
 	    my $patch_line = $_;
-	    if (m/^\+\+\+\s+(\S+)/) {
+	    if (m/^\+\+\+\s+(\S+)/ or m/^---\s+(\S+)/) {
 		my $filename = $1;
 		$filename =~ s@^[^/]*/@@;
 		$filename =~ s@\n@@;