Add cast in stack allocation for task creation (#1340)

for negative portSTACK_GROWTH, add cast to stack allocation, just like it is in positive portSTACK_GROWTH

tasks.c

diff --git a/tasks.c b/tasks.c
index 104ea61..6a52398 100644
--- a/tasks.c
+++ b/tasks.c
@@ -1689,7 +1689,7 @@
             /* MISRA Ref 11.5.1 [Malloc memory assignment] */
             /* More details at: https://github.com/FreeRTOS/FreeRTOS-Kernel/blob/main/MISRA.md#rule-115 */
             /* coverity[misra_c_2012_rule_11_5_violation] */
-            pxStack = pvPortMallocStack( ( ( ( size_t ) uxStackDepth ) * sizeof( StackType_t ) ) );
+            pxStack = ( StackType_t * ) pvPortMallocStack( ( ( ( size_t ) uxStackDepth ) * sizeof( StackType_t ) ) );
 
             if( pxStack != NULL )
             {