slimbus: Disconnect source port if source end is removed by client

If source end of a channel removes its vote, it should be allowed to
be reclaimed by other client (or by other source port by same client)
who wants to be the source for this channel.

CRs-Fixed: 376731
Change-Id: Ia30c6a4b07de7df98cde8bc928205b4f4598036d
Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>