exynos: Cleanup exynos_init

- None of the callers perform error checking and based on the non-empty
  versions of this function, there's no checking to be done, so make
  this a void.
- Add a default weak version of the function.
- Remove the empty versions of exynos_init now that we have a weak
  version.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/mach-exynos/include/mach/board.h b/arch/arm/mach-exynos/include/mach/board.h
index 44ebdb8..a167f96 100644
--- a/arch/arm/mach-exynos/include/mach/board.h
+++ b/arch/arm/mach-exynos/include/mach/board.h
@@ -11,7 +11,7 @@
  * Exynos baord specific changes for
  * board_init
  */
-int exynos_init(void);
+void exynos_init(void);
 
 /*
  * Exynos board specific changes for