mux: mmio: Fix IS_ERR() vs NULL check in probe()

The devm_kmalloc() function never returns error pointers, it returns
NULL on error. Fix the error checking.

Fixes: 4863cb2b0f50 ("mux: mmio: Add suspend and resume support")
Signed-off-by: Dan Carpenter <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/mux/mmio.c

···
 	mux_mmio = mux_chip_priv(mux_chip);
 
 	mux_mmio->fields = devm_kmalloc(dev, num_fields * sizeof(*mux_mmio->fields), GFP_KERNEL);
-	if (IS_ERR(mux_mmio->fields))
-		return PTR_ERR(mux_mmio->fields);
+	if (!mux_mmio->fields)
+		return -ENOMEM;
 
 	mux_mmio->hardware_states = devm_kmalloc(dev, num_fields *
 						 sizeof(*mux_mmio->hardware_states), GFP_KERNEL);
-	if (IS_ERR(mux_mmio->hardware_states))
-		return PTR_ERR(mux_mmio->hardware_states);
+	if (!mux_mmio->hardware_states)
+		return -ENOMEM;
 
 	for (i = 0; i < num_fields; i++) {
 		struct mux_control *mux = &mux_chip->mux[i];