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/trats2/trats2.c b/board/samsung/trats2/trats2.c
index 93c9714..81ccc12 100644
--- a/board/samsung/trats2/trats2.c
+++ b/board/samsung/trats2/trats2.c
@@ -107,7 +107,7 @@
 	return 0;
 }
 
-int exynos_init(void)
+void exynos_init(void)
 {
 	struct exynos4_power *pwr =
 		(struct exynos4_power *)samsung_get_base_power();
@@ -124,8 +124,6 @@
 	 */
 	writel(0, &pwr->inform4);
 	writel(0, &pwr->inform5);
-
-	return 0;
 }
 
 int exynos_power_init(void)