net: gem: Check rate before setting it up

On QEMU setting rate for fixed clock is failing. That's why check a rate
first if the rate is the same there is no need to ask for the change.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/bc465ffd4904bfd65208b782daa06732b915db54.1661502645.git.michal.simek@amd.com
diff --git a/drivers/net/zynq_gem.c b/drivers/net/zynq_gem.c
index 4e8dd4b..61a6c83 100644
--- a/drivers/net/zynq_gem.c
+++ b/drivers/net/zynq_gem.c
@@ -500,10 +500,13 @@
 	}
 #endif
 
-	ret = clk_set_rate(&priv->tx_clk, clk_rate);
-	if (IS_ERR_VALUE(ret)) {
-		dev_err(dev, "failed to set tx clock rate\n");
-		return ret;
+	ret = clk_get_rate(&priv->tx_clk);
+	if (ret != clk_rate) {
+		ret = clk_set_rate(&priv->tx_clk, clk_rate);
+		if (IS_ERR_VALUE(ret)) {
+			dev_err(dev, "failed to set tx clock rate %ld\n", clk_rate);
+			return ret;
+		}
 	}
 
 	ret = clk_enable(&priv->tx_clk);