rpmsg: smd: do not use mananged resources for endpoints and channels

All the managed resources would be freed by the time release function
is invoked. Handling such memory in qcom_smd_edge_release() would do
bad things.

Found this issue while testing Audio usecase where the dsp is started up
and shutdown in a loop.

This patch fixes this issue by using simple kzalloc for allocating
channel->name and channel which is then freed in qcom_smd_edge_release().

Without this patch restarting a remoteproc would crash the system.
Fixes: 53e2822e ("rpmsg: Introduce Qualcomm SMD backend")
Cc: <stable@vger.kernel.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>