compiler.h: add __weak macro

Instead of writing out '__attribute__((weak))' use a shorter form.

Change-Id: If418a1d55052780077febd2d8f2089021f414b91
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/25767
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Justin TerAvest <teravest@chromium.org>

src/drivers/intel/fsp2_0/graphics.c

@@ -124,7 +124,7 @@ int fill_lb_framebuffer(struct lb_framebuffer *framebuffer)
 	return 0;
 }
 
-__attribute__((weak)) uintptr_t fsp_soc_get_igd_bar(void)
+__weak uintptr_t fsp_soc_get_igd_bar(void)
 {
 	return 0;
 }

src/drivers/intel/fsp2_0/hob_display.c

@@ -157,7 +157,7 @@ const char *fsp_get_guid_name(const uint8_t *guid)
 	return "Unknown GUID";
 }
 
-__attribute__((weak)) const char *soc_get_hob_type_name(
+__weak const char *soc_get_hob_type_name(
 	const struct hob_header *hob)
 {
 	return NULL;
@@ -173,7 +173,7 @@ void fsp_print_guid_extension_hob(const struct hob_header *hob)
 	printk(BIOS_SPEW, ": %s\n", fsp_get_guid_name(res->owner_guid));
 }
 
-__attribute__((weak)) const char *soc_get_guid_name(const uint8_t *guid)
+__weak const char *soc_get_guid_name(const uint8_t *guid)
 {
 	return NULL;
 }
@@ -212,6 +212,6 @@ void fsp_display_hobs(void)
 	}
 }
 
-__attribute__((weak)) void soc_display_hob(const struct hob_header *hob)
+__weak void soc_display_hob(const struct hob_header *hob)
 {
 }

src/drivers/intel/fsp2_0/memory_init.c

@@ -307,13 +307,13 @@ static enum cb_err fsp_fill_common_arch_params(FSPM_ARCH_UPD *arch_upd,
 	return CB_SUCCESS;
 }
 
-__attribute__((weak))
+__weak
 uint8_t fsp_memory_mainboard_version(void)
 {
 	return 0;
 }
 
-__attribute__((weak))
+__weak
 uint8_t fsp_memory_soc_version(void)
 {
 	return 0;

src/drivers/intel/fsp2_0/notify.c

@@ -12,6 +12,7 @@
 
 #include <arch/cpu.h>
 #include <bootstate.h>
+#include <compiler.h>
 #include <console/console.h>
 #include <fsp/util.h>
 #include <soc/intel/common/util.h>
@@ -87,7 +88,7 @@ BOOT_STATE_INIT_ENTRY(BS_PAYLOAD_LOAD, BS_ON_EXIT, fsp_notify_dummy,
 BOOT_STATE_INIT_ENTRY(BS_OS_RESUME, BS_ON_ENTRY, fsp_notify_dummy,
 						(void *) READY_TO_BOOT);
 
-__attribute__((weak)) void platform_fsp_notify_status(
+__weak void platform_fsp_notify_status(
 	enum fsp_notify_phase phase)
 {
 }

src/drivers/intel/fsp2_0/upd_display.c

@@ -10,6 +10,7 @@
  */
 
 #include <arch/cpu.h>
+#include <compiler.h>
 #include <console/console.h>
 #include <fsp/util.h>
 #include <lib.h>
@@ -50,7 +51,7 @@ static void fspm_display_arch_params(const FSPM_ARCH_UPD *old,
 }
 
 /* Display the UPD parameters for MemoryInit */
-__attribute__((weak)) void soc_display_fspm_upd_params(
+__weak void soc_display_fspm_upd_params(
 	const FSPM_UPD *fspm_old_upd,
 	const FSPM_UPD *fspm_new_upd)
 {
@@ -67,7 +68,7 @@ void fspm_display_upd_values(const FSPM_UPD *old,
 }
 
 /* Display the UPD parameters for SiliconInit */
-__attribute__((weak)) void soc_display_fsps_upd_params(
+__weak void soc_display_fsps_upd_params(
 	const FSPS_UPD *fsps_old_upd,
 	const FSPS_UPD *fsps_new_upd)
 {