ARM: exynos: move debug-macro.S to include/debug/

The move is necessary to support early debug output on exynos
with multiplatform configurations. This implies also moving the
plat/debug-macro.S file, but we are leaving the remaining users of that
file in place, to avoid adding large numbers of extra configuration
options to Kconfig.debug

Signed-off-by: Arnd Bergmann <arnd@arndb.de>