CMSIS: define osSysTickRateHz in CMSIS headers

This requires that the application define configSPAN_SYS_TICK_RATE_HZ.
We primarily need it because we need an integer literal for defining
a std::chrono-style clock based on the "SysTick".

Note that this updates both copies of the "control blocks" header. I'm
not sure why we have two.

CMSIS/RTOS2/FreeRTOS/Include/cmsis_os2_control_blocks.h

@@ -17,6 +17,11 @@
 #define osTickRateHz (configTICK_RATE_HZ)
 #define osMaxDelayTicks (portMAX_DELAY)
 
+#ifndef configSPAN_SYS_TICK_RATE_HZ
+#error configSPAN_SYS_TICK_RATE_HZ must be defined to a literal integer
+#endif
+#define osSysTickRateHz (configSPAN_SYS_TICK_RATE_HZ)
+
 typedef StaticTask_t osThreadControlBlock;
 typedef MemPool_t osMemoryPoolControlBlock;
 typedef StaticQueue_t osMessageQueueControlBlock;

CMSIS/RTOS2/FreeRTOS/Include/os2_control_blocks.h

@@ -17,6 +17,11 @@
 #define osTickRateHz (configTICK_RATE_HZ)
 #define osMaxDelayTicks (portMAX_DELAY)
 
+#ifndef configSPAN_SYS_TICK_RATE_HZ
+#error configSPAN_SYS_TICK_RATE_HZ must be defined to a literal integer
+#endif
+#define osSysTickRateHz (configSPAN_SYS_TICK_RATE_HZ)
+
 typedef MemPool_t MemoryPoolControlBlock;
 typedef StaticQueue_t MessageQueueControlBlock;