archs38: Add patch for gcc8 compilance

Building Linux kernel version 5.4.x with GCC8 ends up
with internal compiler error. The workaround on this issue
can be introdution of additional compiler option "--mmpy-option=2"

Signed-off-by: Evgeniy Didin <Evgeniy.Didin@synopsys.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Petr Štetiar <ynezz@true.cz>
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Cc: John Crispin <john@phrozen.org>

target/linux/archs38/patches-5.4/0001-arch-arc-Add-compiler-option-for-gcc8.4.patch

@@ -0,0 +1,21 @@
+From 2e2b3aeda9af9c029bf347c974911fe96cd79c43 Mon Sep 17 00:00:00 2001
+From: Evgeniy Didin <didin@synopsys.com>
+Date: Mon, 23 Mar 2020 15:57:18 +0300
+Subject: [PATCH] arch/arc: Add compiler option for gcc8.4
+
+Signed-off-by: Evgeniy Didin <didin@synopsys.com>
+---
+ arch/arc/Makefile | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/arch/arc/Makefile
++++ b/arch/arc/Makefile
+@@ -11,7 +11,7 @@ endif
+ 
+ cflags-y	+= -fno-common -pipe -fno-builtin -mmedium-calls -D__linux__
+ cflags-$(CONFIG_ISA_ARCOMPACT)	+= -mA7
+-cflags-$(CONFIG_ISA_ARCV2)	+= -mcpu=hs38
++cflags-$(CONFIG_ISA_ARCV2)	+= -mcpu=hs38 -mmpy-option=2
+ 
+ ifdef CONFIG_ARC_CURR_IN_REG
+ # For a global register defintion, make sure it gets passed to every file