iwlwifi: update trans->hw_rev 8000 hw family format

The format of the CSR_HW_REV register has changed in 8000
HW family. To keep backwards compatibility, we store the
value of this register as usual in trans->hw_rev, only we
store it in the old format in this variable.

Signed-off-by: Liad Kaufman <liad.kaufman@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>