configs: lp3_emmc-tb: disable low power detect in spl

Change-Id: Ifc5707daf49d1a1abb246a32dc31e5bc43e07274
Signed-off-by: Ziyuan Xu <xzy.xu@rock-chips.com>

configs: add new configuration for lp3_emmc-tb boards

Overlay from rv1126-emmc-tb.config

Signed-off-by: Ziyuan Xu <xzy.xu@rock-chips.com>
Change-Id: Ic0b26dc2934b1ff87d6120e8a66078639f0e1e23