remoteproc/omap: Add watchdog functionality for remote processors

remoteproc/omap: Add watchdog functionality for remote processors

Remote processors can be stuck in a loop, and may not be recoverable
if they do not have a built-in watchdog. The watchdog implementation
for OMAP remote processors uses external gptimers that can be used
to interrupt both the Linux host as well as the remote processor.

Each remote processor is responsible for refreshing the timer during
normal behavior - during OS task scheduling or entering the idle loop
properly. During a watchdog condition (executing a tight loop causing
no scheduling), the host processor gets interrupts and schedules a
recovery for the corresponding remote processor. The remote processor
may also get interrupted to be able to print a back trace.

A menuconfig option has also been added to enable/disable the Watchdog
functionality, with the default as disabled.

Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Reviewed-by: Andrew F. Davis <afd@ti.com>
Link: https://lore.kernel.org/r/20200324110035.29907-15-t-kristo@ti.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>