ACPI: Add acpi_is_wakeup_s3()

Test explicitly for S3 resume.
Also switch to use IS_ENABLED().

Change-Id: I17ea729f51f99ea8d6135f2c7a807623f1286238
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/6070
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

src/arch/x86/boot/acpi.c

@@ -651,6 +651,11 @@ int acpi_is_wakeup(void)
 	return (acpi_slp_type == 3 || acpi_slp_type == 2);
 }
 
+int acpi_is_wakeup_s3(void)
+{
+	return (acpi_slp_type == 3);
+}
+
 void acpi_fail_wakeup(void)
 {
 	if (acpi_slp_type == 3 || acpi_slp_type == 2)