Load/store exception handler: handle re-entry via a NMI.
Load/store exception handler: handle re-entry via a NMI.

The NMI can asynchronously interrupt the load/store exception handler. This
does occur frequently as the NMI handler code does invoke load/store
exceptions, and the load/store exception handler is heavly used. This was
corrupting the load/store exception handler saved state and thus randomly
corrupting registers a0 to a6 of the interruptee.

ourairquality/esp-open-rtos,ourairquality/esp-open-rtos,ourairquality/esp-open-rtos,ourairquality/esp-open-rtos,ourairquality/esp-open-rtos,ourairquality/esp-open-rtos