soc/amd/stoneyridge: Improve code quality

Remove empty functions. In function pointer structure
"device_operations", replace the 0 equality by NULL equality.
Files: hda.c, sata.c and usb.c

Change-Id: I9f8dc7681ab2e651872e69a8b2e990e59ebe80c9
Signed-off-by: Richard Spiegel <richard.spiegel@amd.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/21522
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/stoneyridge/hda.c

@@ -28,10 +28,6 @@ static const unsigned short pci_device_ids[] = {
 	0
 };
 
-static void hda_init(struct device *dev)
-{
-}
-
 static struct pci_operations lops_pci = {
 	.set_subsystem = pci_dev_set_subsystem,
 };
@@ -40,8 +36,8 @@ static struct device_operations hda_audio_ops = {
 	.read_resources = pci_dev_read_resources,
 	.set_resources = pci_dev_set_resources,
 	.enable_resources = pci_dev_enable_resources,
-	.init = hda_init,
-	.scan_bus = 0,
+	.init = NULL,
+	.scan_bus = NULL,
 	.ops_pci = &lops_pci,
 };
 

src/soc/amd/stoneyridge/sata.c

@@ -63,7 +63,7 @@ static struct device_operations sata_ops = {
 	.set_resources = pci_dev_set_resources,
 	.enable_resources = pci_dev_enable_resources,
 	.init = sata_init,
-	.scan_bus = 0,
+	.scan_bus = NULL,
 	.ops_pci = &lops_pci,
 };
 

src/soc/amd/stoneyridge/usb.c

@@ -26,16 +26,12 @@ static struct pci_operations lops_pci = {
 	.set_subsystem = pci_dev_set_subsystem,
 };
 
-static void usb_init(struct device *dev)
-{
-}
-
 static struct device_operations usb_ops = {
 	.read_resources = pci_ehci_read_resources,
 	.set_resources = pci_dev_set_resources,
 	.enable_resources = pci_dev_enable_resources,
-	.init = usb_init,
-	.scan_bus = 0,
+	.init = NULL,
+	.scan_bus = NULL,
 	.ops_pci = &lops_pci,
 };