remoteproc/omap: Check for undefined mailbox messages

Add some checks in the mailbox callback function to limit
any processing in the mailbox callback function to only
certain currently valid messages, and drop all the remaining
messages. A debug message is added to print any such invalid
messages when the appropriate trace control is enabled.

Co-developed-by: Subramaniam Chanderashekarapuram <subramaniam.ca@ti.com>
Signed-off-by: Subramaniam Chanderashekarapuram <subramaniam.ca@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Andrew F. Davis <afd@ti.com>
Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200324110035.29907-10-t-kristo@ti.com


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>