Drop unnecessary DEVICE_NOOP entries

Providing an explicit no-op function pointer is only necessary for
`.read_resources` and `.set_resources`. All other device-operation
pointers are optional and can be NULL.

Change-Id: I3d139f7be86180558cabec04b8566873062e33be
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40206
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/skylake/chip.c

@@ -97,8 +97,6 @@ static struct device_operations pci_domain_ops = {
 static struct device_operations cpu_bus_ops = {
 	.read_resources   = DEVICE_NOOP,
 	.set_resources    = DEVICE_NOOP,
-	.enable_resources = DEVICE_NOOP,
-	.init             = DEVICE_NOOP,
 #if CONFIG(HAVE_ACPI_TABLES)
 	.acpi_fill_ssdt   = generate_cpu_entries,
 #endif