Fix issues found by coverity

Fix one "Uninitialized scalar variable" and two "Out-of-bounds read"

Author: Arto Kinnunen

source/6LoWPAN/ws/ws_pae_nvm_store.c

@@ -161,6 +161,7 @@ static int8_t ws_pae_nvm_store_read(const char *file_name, nvm_tlv_list_t *tlv_l
 
     while (list_count-- > 0) {
         nvm_tlv_entry_t entry_header;
+        memset(&entry_header, 0, sizeof(nvm_tlv_entry_t));
         n_bytes = fread(&entry_header.tag, 1, NVM_TLV_FIXED_LEN, fp);
         if (n_bytes != NVM_TLV_FIXED_LEN) {
             failure = true;

source/Security/protocols/sec_prot_keys.c

@@ -191,7 +191,7 @@ void sec_prot_keys_gtkl_set(sec_prot_gtk_keys_t *gtks, uint8_t gtkl)
 
 bool sec_prot_keys_gtk_is_live(sec_prot_gtk_keys_t *gtks, uint8_t index)
 {
-    if (index > GTK_NUM || !gtks->gtk[index].live) {
+    if (index >= GTK_NUM || !gtks->gtk[index].live) {
         return false;
     }
 
@@ -200,7 +200,7 @@ bool sec_prot_keys_gtk_is_live(sec_prot_gtk_keys_t *gtks, uint8_t index)
 
 int8_t sec_prot_keys_gtk_insert_index_set(sec_prot_gtk_keys_t *gtks, uint8_t index)
 {
-    if (index > GTK_NUM || !gtks->gtk[index].set) {
+    if (index >= GTK_NUM || !gtks->gtk[index].set) {
         return -1;
     }