slimbus: Refine scope of controller and scheduler mutex locks

Controller mutex scope is restricted to controller specific data
structures, such as addressing table, transaction table.
Scheduler lock is used to protect scheduling data structures (such
as channels, and bandwidth).
This way, controller mutex is not needed when expensive
reconfiguration sequence(used for channel scheduling, bandwidth
management) is in progress. Transactions over messaging channel (such
as element read/writes, logical address assignment) can happen in
parallel and don't have to block on reconfiguration sequence which
only affects data channels.

CRs-Fixed: 426945
Change-Id: I2ca20aa76901ee19dba62874c86c2108fac9fa02
Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>