soc: qcom: glink: Add new APIs to toggle RX thread priority

Low latency use cases are failing because glink RX thread to handle
the TX Done command is not being scheduled during high system load.
These new APIs allow clients to specify if they need the RX glink
thread to be Realtime

CRs-Fixed: 2050701
Change-Id: I6bd4023394e9ee617797826687f34abaee3fe65d
Signed-off-by: Chris Lew <clew@codeaurora.org>