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/board/samsung/odroid/odroid.c b/board/samsung/odroid/odroid.c
index d237828..99e5613 100644
--- a/board/samsung/odroid/odroid.c
+++ b/board/samsung/odroid/odroid.c
@@ -423,11 +423,9 @@
 	return 0;
 }
 
-int exynos_init(void)
+void exynos_init(void)
 {
 	board_gpio_init();
-
-	return 0;
 }
 
 int exynos_power_init(void)