sunrpc: convert to time64_t for expiry

Using signed 32-bit types for UTC time leads to the y2038 overflow,
which is what happens in the sunrpc code at the moment.

This changes the sunrpc code over to use time64_t where possible.
The one exception is the gss_import_v{1,2}_context() function for
kerberos5, which uses 32-bit timestamps in the protocol. Here,
we can at least treat the numbers as 'unsigned', which extends the
range from 2038 to 2106.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

include/linux/sunrpc/gss_krb5.h

@@ -106,9 +106,9 @@ struct krb5_ctx {
 	struct crypto_sync_skcipher *initiator_enc_aux;
 	u8			Ksess[GSS_KRB5_MAX_KEYLEN]; /* session key */
 	u8			cksum[GSS_KRB5_MAX_KEYLEN];
-	s32			endtime;
 	atomic_t		seq_send;
 	atomic64_t		seq_send64;
+	time64_t		endtime;
 	struct xdr_netobj	mech_used;
 	u8			initiator_sign[GSS_KRB5_MAX_KEYLEN];
 	u8			acceptor_sign[GSS_KRB5_MAX_KEYLEN];