cifs: decoding negTokenInit with generic ASN1 decoder

Decode negTokenInit with lib/asn1_decoder. For that,
add OIDs in linux/oid_registry.h and a negTokenInit
ASN1 file, "spnego_negtokeninit.asn1".
And define decoder's callback functions, which
are the gssapi_this_mech for checking SPENGO oid and
the neg_token_init_mech_type for getting authentication
mechanisms supported by a server.

Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>

fs/cifs/Kconfig

@@ -19,6 +19,8 @@ config CIFS
 	select CRYPTO_LIB_DES
 	select KEYS
 	select DNS_RESOLVER
+	select ASN1
+	select OID_REGISTRY
 	help
 	  This is the client VFS module for the SMB3 family of NAS protocols,
 	  (including support for the most recent, most secure dialect SMB3.1.1)

fs/cifs/Makefile

@@ -5,13 +5,15 @@
 ccflags-y += -I$(src)		# needed for trace events
 obj-$(CONFIG_CIFS) += cifs.o
 
+$(obj)/spnego_negtokeninit.asn1.o: $(obj)/spnego_negtokeninit.asn1.c $(obj)/spnego_negtokeninit.asn1.h
+
 cifs-y := trace.o cifsfs.o cifssmb.o cifs_debug.o connect.o dir.o file.o \
 	  inode.o link.o misc.o netmisc.o smbencrypt.o transport.o asn1.o \
 	  cifs_unicode.o nterr.o cifsencrypt.o \
 	  readdir.o ioctl.o sess.o export.o smb1ops.o unc.o winucase.o \
 	  smb2ops.o smb2maperror.o smb2transport.o \
 	  smb2misc.o smb2pdu.o smb2inode.o smb2file.o cifsacl.o fs_context.o \
-	  dns_resolve.o
+	  dns_resolve.o spnego_negtokeninit.asn1.o
 
 cifs-$(CONFIG_CIFS_XATTR) += xattr.o