[CIFS] Fix SMB2 negotiation support to select only one dialect (based on vers=)

Based on whether the user (on mount command) chooses:

vers=3.0 (for smb3.0 support)
vers=2.1 (for smb2.1 support)
or (with subsequent patch, which will allow SMB2 support)
vers=2.0 (for original smb2.02 dialect support)

send only one dialect at a time during negotiate (we
had been sending a list).

Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/smb2pdu.h

@@ -163,9 +163,15 @@ struct smb2_negotiate_req {
 	__le32 Capabilities;
 	__u8   ClientGUID[SMB2_CLIENT_GUID_SIZE];
 	__le64 ClientStartTime;	/* MBZ */
-	__le16 Dialects[2]; /* variable length */
+	__le16 Dialects[1]; /* One dialect (vers=) at a time for now */
 } __packed;
 
+/* Dialects */
+#define SMB20_PROT_ID 0x0202
+#define SMB21_PROT_ID 0x0210
+#define SMB30_PROT_ID 0x0300
+#define BAD_PROT_ID   0xFFFF
+
 /* SecurityMode flags */
 #define	SMB2_NEGOTIATE_SIGNING_ENABLED	0x0001
 #define SMB2_NEGOTIATE_SIGNING_REQUIRED	0x0002
@@ -173,6 +179,10 @@ struct smb2_negotiate_req {
 #define SMB2_GLOBAL_CAP_DFS		0x00000001
 #define SMB2_GLOBAL_CAP_LEASING		0x00000002 /* Resp only New to SMB2.1 */
 #define SMB2_GLOBAL_CAP_LARGE_MTU	0X00000004 /* Resp only New to SMB2.1 */
+#define SMB2_GLOBAL_CAP_MULTI_CHANNEL	0x00000008 /* New to SMB3 */
+#define SMB2_GLOBAL_CAP_PERSISTENT_HANDLES 0x00000010 /* New to SMB3 */
+#define SMB2_GLOBAL_CAP_DIRECTORY_LEASING  0x00000020 /* New to SMB3 */
+#define SMB2_GLOBAL_CAP_ENCRYPTION	0x00000040 /* New to SMB3 */
 /* Internal types */
 #define SMB2_NT_FIND			0x00100000
 #define SMB2_LARGE_FILES		0x00200000