TD-BWE state memories reset simplification

The following core-coder TD-BWE code-block is present at seven different paces at the encoder:

set_f( st->hBWE_TD->old_speech_shb, 0.0f, L_LOOK_16k + L_SUBFR16k );
set_f( st->hBWE_TD->mem_shb_res, 0.0f, MAX_LEN_MA_FILTER );
set_f( st->hBWE_TD->old_EnvSHBres, 0.0f, L_FRAME4k );
st->hBWE_TD->old_mean_EnvSHBres = 0.0f;
st->hBWE_TD->prev_enr_EnvSHBres = 1.0f;
st->hBWE_TD->prev_shb_env_tilt = 0.0f;
st->hBWE_TD->prev_pow_exc16kWhtnd = 1.0f;
st->hBWE_TD->prev_mix_factor = 1.0f;
st->hBWE_TD->prev_Env_error = 0.0f;

This could be simplified such that it is replaced by a function. Moreover, this rest seems to be done twice in the case of AMR-WB -> EVS switching.