target: Remove hack to make READ CAPACITY(10) lie if thin provisioning is enabled

Remove the hack that has READ CAPACITY(10) return 0xFFFFFFFF as the
number of sectors when thin provisioning is enabled.  This is supposed
to trigger the initiator to use READ CAPACITY(16) in this case so that
it finds out about thin provisioning.  But an initiator that cares about
thin provisioning is going to ask anyway, and an initiator that doesn't
know about READ CAPACITY(16) is going to get the wrong capacity.  So
just have READ CAPACITY(10) return the size it's supposed to.

Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>