NTB: Xeon Doorbell errata workaround

Modifications to the 14th bit of the B2BDOORBELL register will not be
mirrored to the remote system due to a hardware issue.  To get around
the issue, shrink the number of available doorbell bits by 1.  The max
number of doorbells was being used as a way to referencing the Link
Doorbell bit.  Since this would no longer work, the driver must now
explicitly reference that bit.

This does not affect the xeon_errata_workaround case, as it is not using
the b2bdoorbell register.

Signed-off-by: Jon Mason <jon.mason@intel.com>
NTB: Fix ntb_transport link down race

A WARN_ON is being hit in ntb_qp_link_work due to the NTB transport link
being down while the ntb qp link is still active.  This is caused by the
transport link being brought down prior to the qp link worker thread
being terminated.  To correct this, shutdown the qp's prior to bringing
the transport link down.  Also, only call the qp worker thread if it is
in interrupt context, otherwise call the function directly.

Signed-off-by: Jon Mason <jon.mason@intel.com>
NTB: Fix NTB-RP Link Up

The Xeon NTB-RP setup, the transparent side does not get a link up/down
interrupt.  Since the presence of a NTB device on the transparent side
means that we have a NTB link up, we can work around the lack of an
interrupt by simply calling the link up function to notify the upper
layers.

Signed-off-by: Jon Mason <jon.mason@intel.com>