mt2503 只能接听，不能挂断来电

[DESCRIPTION]
BT Dialer显示来电画面之后，只能接听，不能挂断
[SOLUTION]
低端手机不支持AT+CHLD命令，改用AT+CHUP挂断来电
请在UcmkernelBT.c文件MMI_ucm_end_option_bt()函数中添加一个条件：
int mmi_ucm_end_option_bt(void)
{
//....
if (mmi_ucm_get_call_count_bt() ==
mmi_ucm_query_call_count_by_call_state_bt(SRV_UCM_BT_ACTIVE_STATE, NULL)) // 添加此处
{
result = srv_bt_dialer_hangup_current_call(srv_hd);// 添加此处
}
else if(g_ucm_call_state[g_ucm_p_bt->hilite_tab].call_state == SRV_UCM_BT_HOLD_STATE)//
改为else if
{
result = srv_bt_dialer_release_all_held_calls(srv_hd);
}
//....
}