execve: Reinitialize vm_regions's map area on execve

Reinitialize vm->region.map_end in sys_execve()
in the same way as when creating a new process.

Change-Id: I7fc048a187e619ba4b5a578976e2a6774d13a6a7

kernel/syscall.c

@@ -2135,6 +2135,9 @@ static void munmap_all(void)
 	/* free vm_ranges which do_munmap() failed to remove. */
 	free_process_memory_ranges(thread->vm);
 
+	/* reset vm_region's map area */
+	thread->vm->region.map_end = thread->vm->region.map_start;
+
 	return;
 } /* munmap_all() */