powerpc/hw_brk: Fix clearing of extraneous IRQ

In 9422de3e "powerpc: Hardware breakpoints rewrite to handle non DABR breakpoint
registers" we changed the way we mark extraneous irqs with this:

-	info->extraneous_interrupt = !((bp->attr.bp_addr <= dar) &&
-			(dar - bp->attr.bp_addr < bp->attr.bp_len));
+	if (!((bp->attr.bp_addr <= dar) &&
+	      (dar - bp->attr.bp_addr < bp->attr.bp_len)))
+		info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;

Unfortunately this is bogus as it never clears extraneous IRQ if it's already
set.

This correctly clears extraneous IRQ before possibly setting it.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Reported-by: Edjunior Barbosa Machado <emachado@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/hw_breakpoint.c

@@ -250,6 +250,7 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
 	 * we still need to single-step the instruction, but we don't
 	 * generate an event.
 	 */
+	info->type &= ~HW_BRK_TYPE_EXTRANEOUS_IRQ;
 	if (!((bp->attr.bp_addr <= dar) &&
 	      (dar - bp->attr.bp_addr < bp->attr.bp_len)))
 		info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;