use ASM_NL instead of '; ' for assembler new line character in the macro

For some assemblers, they use another character as newline in a macro
(e.g. arc uses '`'), so for generic assembly code, need use ASM_NL (a
macro) instead of ';' for it.

Basically this is the same patch as applied to Linux kernel -
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/include/linux/linkage.h?id=9df62f054406992ce41ec4558fca6a0fa56fffeb

but modified a bit to fit in U-Boot.

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@ti.com>
diff --git a/arch/arc/include/asm/linkage.h b/arch/arc/include/asm/linkage.h
new file mode 100644
index 0000000..2d1a603
--- /dev/null
+++ b/arch/arc/include/asm/linkage.h
@@ -0,0 +1,12 @@
+/*
+ * Copyright (C) 2004, 2007-2010, 2011-2015 Synopsys, Inc. All rights reserved.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __ASM_ARC_LINKAGE_H
+#define __ASM_ARC_LINKAGE_H
+
+#define ASM_NL		 `	/* use '`' to mark new line in macro */
+
+#endif /* __ASM_ARC_LINKAGE_H */