nfsd: remove unused function

Fix the following clang warning:

fs/nfsd/nfs4state.c:6276:1: warning: unused function 'end_offset'
[-Wunused-function].

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4state.c

@@ -6288,15 +6288,6 @@ out:
 	return status;
 }
 
-static inline u64
-end_offset(u64 start, u64 len)
-{
-	u64 end;
-
-	end = start + len;
-	return end >= start ? end: NFS4_MAX_UINT64;
-}
-
 /* last octet in a range */
 static inline u64
 last_byte_offset(u64 start, u64 len)