lockdep, bug: Exclude TAINT_FIRMWARE_WORKAROUND from disabling lockdep

It's unlikely that TAINT_FIRMWARE_WORKAROUND causes false
lockdep messages, so do not disable lockdep in that case.
We still want to keep lockdep disabled in the
TAINT_OOT_MODULE case:

  - bin-only modules can cause various instabilities in
    their and in unrelated kernel code

  - they are impossible to debug for kernel developers

  - they also typically do not have the copyright license
    permission to link to the GPL-ed lockdep code.

Suggested-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-xopopjjens57r0i13qnyh2yo@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/panic.c

@@ -240,8 +240,16 @@ void add_taint(unsigned flag)
 	 * Also we want to keep up lockdep for staging development and
 	 * post-warning case.
 	 */
-	if (flag != TAINT_CRAP && flag != TAINT_WARN && __debug_locks_off())
-		printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
+	switch (flag) {
+	case TAINT_CRAP:
+	case TAINT_WARN:
+	case TAINT_FIRMWARE_WORKAROUND:
+		break;
+
+	default:
+		if (__debug_locks_off())
+			printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
+	}
 
 	set_bit(flag, &tainted_mask);
 }