The 'maxchans' count is one more than the number of channels, so
'chancount' never got up to equaling 'maxchans'. As a result,
pcm_makelinks() was never called, and one always had to set the sysctl to
get the /dev/mixer and other symlinks generated in the DEVFS case. Instead,
change the test in pcm_addchan() to call pcm_makelinks() after the first
channel is initialized, since the aliases are linked to channel 0.

Reviewed by: cg