checkpatch: warn on unnecessary line continuations

When the previous line is not a line continuation and the current line has
a line continuation but is not a #define, emit a warning.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -3013,6 +3013,15 @@ sub process {
 					      "Macros with complex values should be enclosed in parenthesis\n" . "$herectx");
 				}
 			}
+
+# check for line continuations outside of #defines
+
+		} else {
+			if ($prevline !~ /^..*\\$/ &&
+			    $line =~ /^\+.*\\$/) {
+				WARN("LINE_CONTINUATIONS",
+				     "Avoid unnecessary line continuations\n" . $herecurr);
+			}
 		}
 
 # do {} while (0) macro tests: