ion: Add reserve function to ion

Rather than requiring each platform call memblock_remove or reserve
from the board file, add this to ion

Change-Id: Ie418a692c13e9e0cfe93ecc83d253d3ce860fc83
Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>

include/linux/ion.h

@@ -86,6 +86,17 @@ struct ion_platform_data {
 	struct ion_platform_heap heaps[];
 };
 
+/**
+ * ion_reserve() - reserve memory for ion heaps if applicable
+ * @data:	platform data specifying starting physical address and
+ *		size
+ *
+ * Calls memblock reserve to set aside memory for heaps that are
+ * located at specific memory addresses or of specfic sizes not
+ * managed by the kernel
+ */
+void ion_reserve(struct ion_platform_data *data);
+
 /**
  * ion_client_create() -  allocate a client and returns it
  * @dev:	the global ion device