drivers/net/r8168.c: Guard against generating power resource

Not all platforms need to generate power resources, but the code does
not get optimized out at build time because the devicetree gets
compiled into a linked list. As this code pulls in some heavy ACPI
dependencies that is even implemented with weak empty function it
makes sense to optimize out this code using a Kconfig constant.

This saves 1.5K in ramstage size on gigabyte/ga-945gcm-s2l.

Change-Id: I82289aa7e6e82318417f3b827b86182891dfc2a6
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58657
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/net/Kconfig

@@ -38,6 +38,13 @@ config RT8168_SET_LED_MODE
 	  Configuration for details. With this flag enabled, the
 	  customized_leds variable will be read from devicetree setting.
 
+config RT8168_GEN_ACPI_POWER_RESOURCE
+	bool
+	default n
+	depends on REALTEK_8168_RESET
+	help
+	  Select this if an ACPI power resource needs to be generated.
+
 config ATHEROS_ATL1E_SETMAC
 	bool
 	help

src/drivers/net/r8168.c

@@ -317,7 +317,7 @@ static void r8168_net_fill_ssdt(const struct device *dev)
 		acpigen_write_name_string("_DDN", dev->chip_ops->name);
 
 	/* Power Resource */
-	if (config->has_power_resource) {
+	if (CONFIG(RT8168_GEN_ACPI_POWER_RESOURCE) && config->has_power_resource) {
 		const struct acpi_power_res_params power_res_params = {
 			.stop_gpio = &config->stop_gpio,
 			.stop_delay_ms = config->stop_delay_ms,

src/mainboard/google/hatch/Kconfig

@@ -9,6 +9,7 @@ config BOARD_GOOGLE_BASEBOARD_PUFF
 	select BOARD_GOOGLE_HATCH_COMMON
 	select RT8168_GET_MAC_FROM_VPD
 	select RT8168_SET_LED_MODE
+	select RT8168_GEN_ACPI_POWER_RESOURCE
 	select ROMSTAGE_SPD_SMBUS
 	select SPD_READ_BY_WORD
 	select SOC_INTEL_CSE_LITE_SKU