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

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 <[email protected]>
Signed-off-by: Alexey Brodkin <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Simon Glass <[email protected]>
Cc: Tom Rini <[email protected]>