ACPICA: Headers: Add RISC-V SBI Subtype to DBG2

ACPICA commit 6f4c900bcf9ca065129353f17a83773aa58095aa

Include the RISC-V SBI debugging subtype as documented in DBG2
dated April 10, 2023 [1].

Link: https://learn.microsoft.com/en-us/windows-hardware/drivers/bringup/acpi-debug-port-table # [1]
Link: https://github.com/acpica/acpica/commit/6f4c900bSigned-off-by: Sia Jee Heng <jeeheng.sia@starfivetech.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/acpi/actbl1.h

@@ -755,6 +755,7 @@ struct acpi_dbg2_device {
 #define ACPI_DBG2_16550_WITH_GAS    0x0012
 #define ACPI_DBG2_SDM845_7_372MHZ   0x0013
 #define ACPI_DBG2_INTEL_LPSS        0x0014
+#define ACPI_DBG2_RISCV_SBI_CON     0x0015
 
 #define ACPI_DBG2_1394_STANDARD     0x0000