net: dsa: bcm_sf2: Add support for optional reset controller line

Grab an optional and exclusive reset controller line for the switch and
manage it during probe/remove functions accordingly. For 7278 devices we
change bcm_sf2_sw_rst() to use the reset controller line since the
WATCHDOG_CTRL register does not reset the switch contrary to stated
documentation.

Signed-off-by: Florian Fainelli <[email protected]>
Reviewed-by: Andrew Lunn <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
diff --git a/drivers/net/dsa/bcm_sf2.h b/drivers/net/dsa/bcm_sf2.h
index 1df30cc..de386dd 100644
--- a/drivers/net/dsa/bcm_sf2.h
+++ b/drivers/net/dsa/bcm_sf2.h
@@ -18,6 +18,7 @@
 #include <linux/types.h>
 #include <linux/bitops.h>
 #include <linux/if_vlan.h>
+#include <linux/reset.h>
 
 #include <net/dsa.h>
 
@@ -64,6 +65,8 @@ struct bcm_sf2_priv {
 	void __iomem			*fcb;
 	void __iomem			*acb;
 
+	struct reset_control		*rcdev;
+
 	/* Register offsets indirection tables */
 	u32 				type;
 	const u16			*reg_offsets;