NTB: ntb_hw_intel: show BAR size in debugfs info

It will be useful to know the hardware configured BAR size to diagnose
issues with NTB memory windows.

Signed-off-by: Allen Hubbe <Allen.Hubbe@emc.com>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>