Blackfin serial driver: add extra IRQ flag for 8250 serial driver

Signed-off-by: Javier Herrero <jherrero@hvsistemas.es>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

diff --git a/include/asm-blackfin/serial.h b/include/asm-blackfin/serial.h
new file mode 100644
index 0000000..994dd86
--- /dev/null
+++ b/include/asm-blackfin/serial.h
@@ -0,0 +1,5 @@
+/*
+ * include/asm-blackfin/serial.h
+ */
+
+#define SERIAL_EXTRA_IRQ_FLAGS IRQF_TRIGGER_HIGH