checkpatch: add exception to return then else test

Add an exception to the return before else warning when the line
following it is also a return like:

	if (foo)
		return bar;
	else
		return baz;

This form of a test then return is at least as readable as

	if (foo)
		return bar;
	return baz;

so don't emit a warning on the first form.

Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Elshad Mustafayev <elshadimo@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2641,10 +2641,14 @@ sub process {
 		next if ($realfile !~ /\.(h|c)$/);
 
 # check indentation of any line with a bare else
+# (but not if it is a multiple line "if (foo) return bar; else return baz;")
 # if the previous line is a break or return and is indented 1 tab more...
 		if ($sline =~ /^\+([\t]+)(?:}[ \t]*)?else(?:[ \t]*{)?\s*$/) {
 			my $tabs = length($1) + 1;
-			if ($prevline =~ /^\+\t{$tabs,$tabs}(?:break|return)\b/) {
+			if ($prevline =~ /^\+\t{$tabs,$tabs}break\b/ ||
+			    ($prevline =~ /^\+\t{$tabs,$tabs}return\b/ &&
+			     defined $lines[$linenr] &&
+			     $lines[$linenr] !~ /^[ \+]\t{$tabs,$tabs}return/)) {
 				WARN("UNNECESSARY_ELSE",
 				     "else is not generally useful after a break or return\n" . $hereprev);
 			}