slimbus: Fix channel concurrent usage during reconfiguration sequence

Reconfiguration sequence can lead to changes in channel segment
distribution and state. Since multiple clients can use 1 channel,
make sure channels cannot be manipulated when reconfiguration
sequence is in progress, and make sure that client doesn't send
reconfiguration sequence when no changes are pending to be sent
in the sequence from it.

CRs-Fixed: 383406
Change-Id: Ib5f0bc32f67f51f118fa417a2e580c8dc87ef0d0
Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>