SUNRPC: Export get_gss_krb5_enctype()

I plan to add KUnit tests that will need enctype profile
information. Export the enctype profile lookup function.

Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>