reset: sunxi: declare sun6i_reset_init in a header file

Avoid declaring extern functions in c files. To make sure function
definition and usage don't get out of sync, declare sun6i_reset_init
in a common header.

Suggested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/reset/reset-sunxi.c

@@ -18,6 +18,7 @@
 #include <linux/of_address.h>
 #include <linux/platform_device.h>
 #include <linux/reset-controller.h>
+#include <linux/reset/sunxi.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>