Drop explicit NULL initializations from device_operations

Unmentioned fields are initialized with 0 (or NULL) implicitly. Beside
that, the struct has grown over the years. There are too many optional
fields to list them all.

Change-Id: Icb9e14c58153d7c14817bcde148e86e977666e4b
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40126
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/apollolake/chip.c

@@ -214,8 +214,6 @@ static void pci_domain_set_resources(struct device *dev)
 static struct device_operations pci_domain_ops = {
 	.read_resources = pci_domain_read_resources,
 	.set_resources = pci_domain_set_resources,
-	.enable_resources = NULL,
-	.init = NULL,
 	.scan_bus = pci_domain_scan_bus,
 	.acpi_name = &soc_acpi_name,
 };
@@ -225,7 +223,6 @@ static struct device_operations cpu_bus_ops = {
 	.set_resources = DEVICE_NOOP,
 	.enable_resources = DEVICE_NOOP,
 	.init = apollolake_init_cpus,
-	.scan_bus = NULL,
 	.acpi_fill_ssdt = generate_cpu_entries,
 };