cifs: spnego: add ';' in HOST_KEY_LEN

"host=" should start with ';' (as in cifs_get_spnego_key)
So its length should be 6.

Found by Linux Verification Center (linuxtesting.org) with SVACE.
Reviewed-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Fixes: 7c9c3760 ("[CIFS] add constants for string lengths of keynames in SPNEGO upcall string")
Signed-off-by: Anastasia Belova <abelova@astralinux.ru>
Co-developed-by: Ekaterina Esina <eesina@astralinux.ru>
Signed-off-by: Ekaterina Esina <eesina@astralinux.ru>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/client/cifs_spnego.c

@@ -64,8 +64,8 @@ struct key_type cifs_spnego_key_type = {
  * strlen(";sec=ntlmsspi") */
 #define MAX_MECH_STR_LEN	13
 
-/* strlen of "host=" */
-#define HOST_KEY_LEN		5
+/* strlen of ";host=" */
+#define HOST_KEY_LEN		6
 
 /* strlen of ";ip4=" or ";ip6=" */
 #define IP_KEY_LEN		5