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) <[e-mail]>
Fixes: 7c9c3760b3a5 ("[CIFS] add constants for string lengths of keynames in SPNEGO upcall string")
Signed-off-by: Anastasia Belova <[e-mail]>
Co-developed-by: Ekaterina Esina <[e-mail]>
Signed-off-by: Ekaterina Esina <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/smb/client/cifs_spnego.c

···
  * 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