mount.nfs: squelch compiler warning for TI-RPC builds

The printf format string in nfs_pp_debug() assumes the @program and
@version arguments are unsigned long, because the legacy RPC headers
define both rpcprog_t and rpcvers_t as unsigned long types.

However, the TI-RPC headers define both types as uint32_t, which
requires a different printf format type.  If we replace the legacy
headers with TI-RPC headers, this type mismatch generates compiler
warnings that are nothing but noise.

We are about to provide a switch at ./configure time to allow the use
of either the legacy RPC headers or the TI-RPC headers, so we need
a printf format that works in both cases.

To squelch the compiler warnings that occur when using the TI-RPC
headers, cast both arguments in the fprintf statement to the widest of
the two types ("unsigned long" or "uint32_t").

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Steve Dickson <steved@redhat.com>