alsa-mixer: Always turn "Inverted Internal Mic" off

alsa-mixer: Always turn "Inverted Internal Mic" off

Some devices have inverted right channel, so when you add left and right,
the result is silence, or very faint sound. In recent kernels (3.5,
perhaps also 3.4) these are starting to be marked with a special
"Inverted Internal Mic" capture switch.

While we might want to add some reverse summing mechanism in the
future, for now, we just turn the thing off to avoid the problem of
recording silence.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>