nptl: Remove g_refs from condition variables

nptl: Remove g_refs from condition variables

This variable used to be needed to wait in group switching until all sleepers
have confirmed that they have woken. This is no longer needed. Nothing waits
on this variable so there is no need to track how many threads are currently
asleep in each group.

Signed-off-by: Malte Skarupke <malteskarupke@fastmail.fm>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>