arc: add architecture header files

These are header files used by ARC700 architecture.

Also note that "arch-arc700/hardware.h" is only required for compilation of
"designware_i2c" driver which refers to "asm/arch/hardware.h".
It would be good to fix mentioned driver sometime soon but it will cause
changes in ARM board configs that use "designware_i2c".

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

Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Francois Bedard <fbedard@synopsys.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Heiko Schocher <hs@denx.de>

arch/arc/include/asm/u-boot-arc.h

@@ -0,0 +1,12 @@
+/*
+ * Copyright (C) 2014 Synopsys, Inc. All rights reserved.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __ASM_ARC_U_BOOT_ARC_H__
+#define __ASM_ARC_U_BOOT_ARC_H__
+
+int arch_early_init_r(void);
+
+#endif	/* __ASM_ARC_U_BOOT_ARC_H__ */