net: Fix static checker warnings

Here are the smatch warning messages:

drivers/net/xilinx_axi_emac.c:324 axiemac_phy_init()
error: 'phydev' dereferencing possible ERR_PTR()

drivers/net/zynq_gem.c:340 zynq_phy_init()
error: 'priv->phydev' dereferencing possible ERR_PTR()

Fix by adding error checking before dereferencing the pointer.

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
Link: https://lore.kernel.org/r/20220929045605.23964-1-venkatesh.abbarapu@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com>
diff --git a/drivers/net/xilinx_axi_emac.c b/drivers/net/xilinx_axi_emac.c
index d48e342..5f5bc65 100644
--- a/drivers/net/xilinx_axi_emac.c
+++ b/drivers/net/xilinx_axi_emac.c
@@ -11,6 +11,7 @@
 #include <cpu_func.h>
 #include <display_options.h>
 #include <dm.h>
+#include <dm/device_compat.h>
 #include <log.h>
 #include <net.h>
 #include <malloc.h>
@@ -317,6 +318,10 @@
 
 	/* Interface - look at tsec */
 	phydev = phy_connect(priv->bus, priv->phyaddr, dev, priv->interface);
+	if (IS_ERR_OR_NULL(phydev)) {
+		dev_err(dev, "phy_connect() failed\n");
+		return -ENODEV;
+	}
 
 	phydev->supported &= supported;
 	phydev->advertising = phydev->supported;