staging: unisys: visorhba: visorhbas_open[] no longer used, so deleted

The prior patch which simplified the visorhba debugfs interface made it so
visorhbas_open[] and VISORHBA_OPEN_MAX were no longer needed, so they have
now been deleted.

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>