Fix isspace() definition

The isspace() function is part of ctype.c/h, remove the conflicting
definition from stdlib.h

Signed-off-by: Balint Dobszay <balint.dobszay@arm.com>
Change-Id: Icff787a28cab2929e5a5212d807f10e3cf06bdcb
diff --git a/components/common/libc/src/strtoull.c b/components/common/libc/src/strtoull.c
index 2e65a43..bd63301 100644
--- a/components/common/libc/src/strtoull.c
+++ b/components/common/libc/src/strtoull.c
@@ -34,6 +34,7 @@
  * SUCH DAMAGE.
  */
 
+#include <ctype.h>
 #include <errno.h>
 #include <limits.h>
 #include <stddef.h>