bnxt_en: Add BNXT_NEW_RM() macro.

The BNXT_FLAG_NEW_RM flag is checked a lot in the code to determine if
the new resource manager is in effect.  Define a macro to perform
this check.

Signed-off-by: Michael Chan <michael.chan@broadocm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>