slim_msm: Support TX message queues

TX message queues are setup using BAM descriptors and event to
notify when the descriptor is done. This type of access ensures
lesser interrupts for slimbus controller, and offloads CPU from
copying message buffer into registers.
At this time, TX message queues are enabled on non-ported generic
device per HW recommendation.

Change-Id: I26423ef4d9fb3d54594d64555417f9a0c1dac37d
Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>