nfsd: return success for non-NFS4 nfs4_state_start

Today's linux-next build (sparc64_defconfig) failed like this:

In file included from arch/sparc/kernel/sys_sparc32.c:32:
include/linux/nfsd/nfsd.h: In function 'nfs4_state_start':
include/linux/nfsd/nfsd.h:177: error: no return statement in function returning non-void

Caused by commit 29ab23cc ("nfsd4: allow
nfs4 state startup to fail").  Please, if you add code that depends on a
CONFIG option, build with that option enabled and disabled.
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

include/linux/nfsd/nfsd.h

@@ -174,7 +174,7 @@ int nfs4_reset_recoverydir(char *recdir);
 #else
 static inline int nfs4_state_init(void) { return 0; }
 static inline void nfsd4_free_slabs(void) { }
-static inline int nfs4_state_start(void) { }
+static inline int nfs4_state_start(void) { return 0; }
 static inline void nfs4_state_shutdown(void) { }
 static inline time_t nfs4_lease_time(void) { return 0; }
 static inline void nfs4_reset_lease(time_t leasetime) { }