thirdparty/dxerr: cast xaudio2 error codes to HRESULT type
thirdparty/dxerr: cast xaudio2 error codes to HRESULT type

Changes:
* thirdparty/dxerr/dxerr.cpp: cast XAUDIO2_E_ defines to HRESULT
which is the result type of the parameter of both DXGetErrorStringA
and DXGetErrorDescriptionA function.

Otherwise, gcc shows error narrowing conversion from int to long.
This casting also matches with WinSDK xaudio2.h file.

apitrace/apitrace,apitrace/apitrace,apitrace/apitrace,apitrace/apitrace