rpmsg: glink: Split rpm_probe to reuse the common code

There is quite some code common in glink_rpm_probe that
can reused for glink-smem based transport as well. So
split the function and move the code to glink_native_probe
that can be used later when we add the support for
glink-smem based transport. Also reuse driver's remove as well.

Change-Id: I84810ba8a11708795ef0ace0ff10a08ca18bea87
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Sricharan R <sricharan@codeaurora.org>