MdePkg: Add new 16550-compatible Serial Port Subtypes to DBG2

MdePkg: Add new 16550-compatible Serial Port Subtypes to DBG2

The Microsoft Debug Port Table 2 (DBG2) specification revision
May 31, 2017 adds support for 16550-compatible Serial Port
Subtype with parameters defined in Generic Address Structure (GAS) [1]

Reflect that in the EDK2 headers.

[1] https://docs.microsoft.com/en-us/windows-hardware/drivers/bringup/acpi-debug-port-table

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@arm.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Sunny Wang <sunny.wang@arm.com>