dt:net:stmmac: Add dt specific phy reset callback support.

This patch adds phy reset callback support for stmmac driver via device
trees. It adds three new properties to gmac device tree bindings to
define the reset signal via gpio.

With this patch users can conveniently pass reset gpio number with pre,
pulse and post delay in micro secs via DTs.

 active low:
		_________		 ____________
	<pre-delay>	|<pulse-delay>	|<post-delay>
		 	|		|
		 	|_______________|

 active high:
 			 ________________
	<pre-delay>	|<pulse-delay>	|<post-delay>
			|		|
		________|		|___________

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
index c1b3ed3..9e495d31 100644
--- a/include/linux/stmmac.h
+++ b/include/linux/stmmac.h
@@ -80,6 +80,10 @@
 	unsigned int phy_mask;
 	int *irqs;
 	int probed_phy_irq;
+#ifdef CONFIG_OF
+	int reset_gpio, active_low;
+	u32 delays[3];
+#endif
 };
 
 struct stmmac_dma_cfg {