TARGET_MCU_NRF51822_UNIFIED - fix ISR stack size (IAR)

Author: mprse

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF51/TARGET_MCU_NRF51822_UNIFIED/device/TOOLCHAIN_IAR/TARGET_MCU_NORDIC_32K/nRF51822_QFAA.icf

@@ -11,8 +11,8 @@ define symbol __ICFEDIT_region_RAM_end__   = 0x20007FFF;
 export symbol __ICFEDIT_region_RAM_start__;
 export symbol __ICFEDIT_region_RAM_end__;
 /*-Sizes-*/
-/*Heap 1/4 of ram and stack 1/8*/
-define symbol __ICFEDIT_size_cstack__   = 0x800;
+/*Heap 1/4 of ram and stack 1024 B */
+define symbol __ICFEDIT_size_cstack__   = 0x400;
 define symbol __ICFEDIT_size_heap__     = 0x1800;
 /**** End of ICF editor section. ###ICF###*/