checkpatch: check for #if 0/#if 1

The #if 0 or #if 1 is used to toggle features. Warn if #if 0 or #if 1
is present and suggest that they can be removed.

[akpm@linux-foundation.org: fix spacing around periods, per Joe\
Link: http://lkml.kernel.org/r/1532625218-24321-1-git-send-email-pheragu@codeaurora.orgSigned-off-by: NAbhijeet Dharmapurikar <adharmap@codeaurora.org>
Signed-off-by: NPrakruthi Deepak Heragu <pheragu@codeaurora.org>
Acked-by: NJoe Perches <joe@perches.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -5422,9 +5422,14 @@ sub process {
 
 # warn about #if 0
 		if ($line =~ /^.\s*\#\s*if\s+0\b/) {
-			CHK("REDUNDANT_CODE",
-			    "if this code is redundant consider removing it\n" .
-				$herecurr);
+			WARN("IF_0",
+			     "Consider removing the code enclosed by this #if 0 and its #endif\n" . $herecurr);
+		}
+
+# warn about #if 1
+		if ($line =~ /^.\s*\#\s*if\s+1\b/) {
+			WARN("IF_1",
+			     "Consider removing the #if 1 and its #endif\n" . $herecurr);
 		}
 
 # check for needless "if (<foo>) fn(<foo>)" uses