checkpatch: add check for whitespace before semicolon at end-of-line

This tests for a bad habits of mine like this:

	return 0 ;

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
diff --git a/tools/checkpatch.pl b/tools/checkpatch.pl
index 2048a44..c7475f9 100755
--- a/tools/checkpatch.pl
+++ b/tools/checkpatch.pl
@@ -3139,6 +3139,12 @@
 			 "Statements terminations use 1 semicolon\n" . $herecurr);
 		}
 
+# check for whitespace before semicolon - not allowed at end-of-line
+		if ($line =~ /\s+;$/) {
+		    WARN("SPACEBEFORE_SEMICOLON",
+			 "Whitespace before semicolon\n" . $herecurr);
+		}
+
 # check for gcc specific __FUNCTION__
 		if ($line =~ /__FUNCTION__/) {
 			WARN("USE_FUNC",