net: stmmac: handle endianness in dwmac4_get_timestamp

GMAC IP is little-endian and used on several kind of CPU (big or little
endian). Main callbacks functions of the stmmac drivers take care about
it. It was not the case for dwmac4_get_timestamp function.

Fixes: ba1ffd74 ("stmmac: fix PTP support for GMAC4")
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c

@@ -241,15 +241,18 @@ static inline void dwmac4_get_timestamp(void *desc, u32 ats, u64 *ts)
 static int dwmac4_rx_check_timestamp(void *desc)
 {
 	struct dma_desc *p = (struct dma_desc *)desc;
+	unsigned int rdes0 = le32_to_cpu(p->des0);
+	unsigned int rdes1 = le32_to_cpu(p->des1);
+	unsigned int rdes3 = le32_to_cpu(p->des3);
 	u32 own, ctxt;
 	int ret = 1;
 
-	own = p->des3 & RDES3_OWN;
-	ctxt = ((p->des3 & RDES3_CONTEXT_DESCRIPTOR)
+	own = rdes3 & RDES3_OWN;
+	ctxt = ((rdes3 & RDES3_CONTEXT_DESCRIPTOR)
 		>> RDES3_CONTEXT_DESCRIPTOR_SHIFT);
 
 	if (likely(!own && ctxt)) {
-		if ((p->des0 == 0xffffffff) && (p->des1 == 0xffffffff))
+		if ((rdes0 == 0xffffffff) && (rdes1 == 0xffffffff))
 			/* Corrupted value */
 			ret = -EINVAL;
 		else