STM32F070RB/STM32F072RB: decrease thread_stack_main size

Thread_stack_main is by default too large for this 16K target

Author: jeromecoutant

rtos/rtx/TARGET_CORTEX_M/RTX_CM_lib.h

@@ -352,6 +352,7 @@ __attribute__((used)) void _mutex_release (OS_ID *mutex) {
 extern void pre_main (void);
 
 #if defined(TARGET_MCU_NRF51822) || defined(TARGET_MCU_NRF52832) || defined (TARGET_STM32F334R8) ||\
+    defined(TARGET_STM32F070RB) || defined(TARGET_STM32F072RB) || \
     defined(TARGET_STM32F302R8) || defined(TARGET_STM32F303K8) || defined (TARGET_STM32F334C8)
 static uint32_t thread_stack_main[DEFAULT_STACK_SIZE / sizeof(uint32_t)];
 #else