Revert "rpmsg: smd: Create device for all channels"

In an effort to pick up channels that are in a funky state we
optimistically tried to open all channels that we found, with the
addition that we failed if the other side did not handshake the opening.

But as we're starting the modem a second time all channels are found -
in a "funky" state - and we try to open them. But the modem firmware
requires the IPCRTR to be up in order to initialize. So any channels we
try to open before that will fail and will not be opened again.

This takes care of the regression, at the cost of reintroducing the
previous behavior of handling of channels with "funky" states.

Reverts commit c12fc451 ("rpmsg: smd: Create device for all channels")

Reported-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>