msdkh265enc: let MSDK select the encoding mode by default
MSDK may support lowpower and non-lowpower modes, some features are available only under one of the two modes, which is hard to know for user, so let MSDK select the mode by default.
MSDK may support lowpower and non-lowpower modes, some features are available only under one of the two modes, which is hard to know for user, so let MSDK select the mode by default.