acpi: Add support for generating ACPI _UPC

This commit adds support for writing ACPI _UPC structures that
help describe USB ports for the OS.

This is a simple structure format which indicates what type of
port it is and whether it is connectable.  It should be paired
with an ACPI _PLD structure to define USB ports for the OS.

Change-Id: Ide3768f60f96e9ad7f919ad3fb11d91045dc174a
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Reviewed-on: https://review.coreboot.org/26170
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/arch/x86/acpigen.c

@@ -1221,6 +1221,21 @@ void acpigen_write_return_string(const char *arg)
 	acpigen_write_string(arg);
 }
 
+void acpigen_write_upc(enum acpi_upc_type type)
+{
+	acpigen_write_name("_UPC");
+	acpigen_write_package(4);
+	/* Connectable */
+	acpigen_write_byte(type == UPC_TYPE_UNUSED ? 0 : 0xff);
+	/* Type */
+	acpigen_write_byte(type);
+	/* Reserved0 */
+	acpigen_write_zero();
+	/* Reserved1 */
+	acpigen_write_zero();
+	acpigen_pop_len();
+}
+
 void acpigen_write_dsm(const char *uuid, void (**callbacks)(void *),
 		       size_t count, void *arg)
 {