sunrpc/cache: simplify cache_fresh_locked and cache_fresh_unlocked.

The extra call to cache_revisit_request in cache_fresh_unlocked is not
needed, as should have been fairly clear at the time of
   commit 4013edea

If there are requests to be revisited, then we can be sure that
CACHE_PENDING is set, so the second call is sufficient.

So remove the first call.
Then remove the 'new' parameter,
then remove the return value for cache_fresh_locked which is only used
to provide the value for 'new'.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>