checkpatch: whinge about bool bitfields

Using bool in a bitfield isn't a good idea as the alignment behavior is
arch implementation defined.

Suggest using unsigned int or u<8|16|32> instead.

Link: http://lkml.kernel.org/r/e22fb871b1b7f2fda4b22f3a24e0d7f092eb612c.camel@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -6251,6 +6251,12 @@ sub process {
 			}
 		}
 
+# check for bool bitfields
+		if ($sline =~ /^.\s+bool\s*$Ident\s*:\s*\d+\s*;/) {
+			WARN("BOOL_BITFIELD",
+			     "Avoid using bool as bitfield.  Prefer bool bitfields as unsigned int or u<8|16|32>\n" . $herecurr);
+		}
+
 # check for semaphores initialized locked
 		if ($line =~ /^.\s*sema_init.+,\W?0\W?\)/) {
 			WARN("CONSIDER_COMPLETION",