Make heap to be of expanding size

Author: Deepika

targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L443xC/device/TOOLCHAIN_IAR/stm32l443xx.icf

@@ -28,7 +28,7 @@ if (!isdefinedsymbol(MBED_BOOT_STACK_SIZE)) {
 define symbol __size_cstack__ = MBED_BOOT_STACK_SIZE;
 define symbol __size_heap__   = 0x4000;
 define block CSTACK    with alignment = 8, size = __size_cstack__   { };
-define block HEAP      with alignment = 8, size = __size_heap__     { };
+define block HEAP      with expanding size, minimum size = __size_heap__, alignment = 8    { };
 define block STACKHEAP with fixed order { block HEAP, block CSTACK };
 
 initialize by copy with packing = zeros { readwrite };

targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L475xG/device/TOOLCHAIN_IAR/stm32l475xx.icf

@@ -37,7 +37,7 @@ if (!isdefinedsymbol(MBED_BOOT_STACK_SIZE)) {
 define symbol __size_cstack__ = MBED_BOOT_STACK_SIZE;
 define symbol __size_heap__   = 0x12000;
 define block CSTACK    with alignment = 8, size = __size_cstack__   { };
-define block HEAP      with alignment = 8, size = __size_heap__     { };
+define block HEAP      with expanding size, minimum size = __size_heap__, alignment = 8   { };
 
 initialize by copy with packing = zeros { readwrite };
 do not initialize  { section .noinit };