checkpatch: report the right line # when using --emacs and --file

commit 34d8815f ("checkpatch: add --showfile to allow input via pipe
to show filenames") broke the --emacs with --file option.

Fix it.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2166,8 +2166,12 @@ sub process {
 		if ($showfile) {
 			$prefix = "$realfile:$realline: "
 		} elsif ($emacs) {
+			if ($file) {
+				$prefix = "$filename:$realline: ";
+			} else {
 				$prefix = "$filename:$linenr: ";
 			}
+		}
 
 		if ($found_file) {
 			if ($realfile =~ m@^(drivers/net/|net/)@) {