simple mixer: fix calculation of control range
simple mixer: fix calculation of control range

When calculating the value range of a control, the variables cannot be
initialized with zero because this would prevent the minimum from having
a value above zero or the maximum from having a value below zero.

mengdonglin/alsa-lib,Distrotech/alsa-lib,mengdonglin/alsa-lib,zedongchen/alsa-lib,alsa-project/alsa-lib,gittup/alsa-lib,alsa-project/alsa-lib,zedongchen/alsa-lib,takaswie/alsa-lib,Distrotech/alsa-lib,mengdonglin/alsa-lib,zedongchen/alsa-lib,gittup/alsa-lib,takaswie/alsa-lib,mengdonglin/alsa-lib,mikelima/alsa-lib,tiwai/alsa-lib,takaswie/alsa-lib,takaswie/alsa-lib,lgirdwood/alsa-lib,Distrotech/alsa-lib,mengdonglin/alsa-lib,mikelima/alsa-lib,alsa-project/alsa-lib,gittup/alsa-lib,Distrotech/alsa-lib,mikelima/alsa-lib,tiwai/alsa-lib,zedongchen/alsa-lib,tiwai/alsa-lib,lgirdwood/alsa-lib,Distrotech/alsa-lib,lgirdwood/alsa-lib,tiwai/alsa-lib,gittup/alsa-lib,mikelima/alsa-lib,zedongchen/alsa-lib,mikelima/alsa-lib,takaswie/alsa-lib,alsa-project/alsa-lib,lgirdwood/alsa-lib,lgirdwood/alsa-lib