NFSD: Fix NFSv3 SETATTR/CREATE's handling of large file sizes

In the Linux kernel, the following vulnerability has been resolved: NFSD: Fix NFSv3 SETATTR/CREATE's handling of large file sizes iattr::ia_size is a loff_t, so these NFSv3 procedures must be careful to deal with incoming client size values that are larger than s64_max without corrupting the value. Silently capping the value results in storing a different value than the client passed in which is unexpected behavior, so remove the min_t() check in decode_sattr3(). Note that RFC 1813 permits only the WRITE procedure to return NFS3ERR_FBIG. We believe that NFSv3 reference implementations also return NFS3ERR_FBIG when ia_size is too large.