arc: move CPU flags selection to the main "config.mk"

As a preparation to ARCv2 port submission we're moving CPU slection
flags to a common location.
Also it will allow us to have more flexible CPU specification, not only
ISA version but CPU family as well checking CONFIG_ARC_CPU_xxx.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

arch/arc/config.mk

@@ -27,8 +27,12 @@ ifdef CONFIG_ARC_MMU_VER
 CONFIG_MMU = 1
 endif
 
+ifdef CONFIG_CPU_ARC750D
+PLATFORM_CPPFLAGS += -marc700
+endif
+
 ifdef CONFIG_CPU_ARC770D
-PLATFORM_CPPFLAGS += -mlock -mswape
+PLATFORM_CPPFLAGS += -marc700 -mlock -mswape
 endif
 
 PLATFORM_CPPFLAGS += -ffixed-r25 -D__ARC__ -gdwarf-2

arch/arc/cpu/arcv1/config.mk

-#
-# Copyright (C) 2013-2014 Synopsys, Inc. All rights reserved.
-#
-# SPDX-License-Identifier:	GPL-2.0+
-#
-
-PLATFORM_CPPFLAGS += -mA7