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.

Acked-by: Arun Kumar Neelakantam <aneela@codeaurora.org>
Signed-off-by: Sricharan R <sricharan@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>