debug: Avoid setting BUGFLAG_WARNING twice

Dan reported that his static checking complains about BUGFLAG_WARNING
being set on both sides of the bitwise-or, it figures that that might've
been an unintentional mistake.

Since there are no architectures that implement __WARN_TAINT() (I
converted them all to implement __WARN_FLAGS()), and all __WARN_FLAGS()
implementations already set BUGFLAG_WARNING, we can remove the bit from
BUGFLAG_TAINT() and make Dan's checker happy.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170410084939.4bwhrvpmauwfzauq@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>