Merge branch 'feature/crosscore_int' into 'master'

Add cross-core int to accelerate task being awoken from another CPU.

This adds a per-CPU interrupt that can be used to poke the CPU to go do something. In this case all that is implemented is a request to yield the current task, used in case a CPU unblocks a task that runs on another CPU. This gets rid of the limitation that inter-CPU communication using queues, muxes etc can take up to a FreeRTOS tick to happen.

Specs!
Sending an in in a queue of length 1 (essentially a semaphore) as quickly as possible (just a small delay in the sender, to make sure the receiver task gets swapped out) for 10 seconds. Number indicates the amount of ints transferred

Old code:

CPU0->CPU0: 42986

CPU0->CPU1,: 2999

New code:

CPU0->CPU0: 42868

CPU0->CPU1: 62073

See merge request !155

components/freertos/include/freertos/FreeRTOSConfig.h

@@ -180,7 +180,7 @@
 /* The Xtensa port uses a separate interrupt stack. Adjust the stack size */
 /* to suit the needs of your specific application.                        */
 #ifndef configISR_STACK_SIZE
-#define configISR_STACK_SIZE			1024//2048
+#define configISR_STACK_SIZE			CONFIG_FREERTOS_ISR_STACKSIZE
 #endif
 
 /* Minimal heap size to make sure examples can run on memory limited

components/freertos/include/freertos/portable.h

@@ -179,6 +179,14 @@ BaseType_t xPortStartScheduler( void ) PRIVILEGED_FUNCTION;
  */
 void vPortEndScheduler( void ) PRIVILEGED_FUNCTION;
 
+
+/*
+ * Send an interrupt to another core in order to make the task running
+ * on it yield for a higher-priority task.
+ */
+
+void vPortYieldOtherCore( BaseType_t coreid) PRIVILEGED_FUNCTION;
+
 /*
  * The structures and methods of manipulating the MPU are contained within the
  * port layer.