SUNRPC: Don't use variable length automatic arrays in kernel code

Replace the variable length array in the RPCSEC_GSS crypto code with
a fixed length one. The size should be bounded by the variable
GSS_KRB5_MAX_BLOCKSIZE, so use that.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --cc net/sunrpc/auth_gss/gss_krb5_crypto.c
Simple merge