stmmac: use one memset() to reset TDES01

Use one memset() to reset all TDES01 fields instead
of one by one to reduce number of instructions.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/stmmac/enh_desc.c b/drivers/net/stmmac/enh_desc.c
index 77ff88c..5d1471d 100644
--- a/drivers/net/stmmac/enh_desc.c
+++ b/drivers/net/stmmac/enh_desc.c
@@ -284,7 +284,7 @@
 {
 	int ter = p->des01.etx.end_ring;
 
-	memset(p, 0, sizeof(struct dma_desc));
+	memset(p, 0, offsetof(struct dma_desc, des2));
 	p->des01.etx.end_ring = ter;
 }