bnxt: use new queue try_stop/try_wake macros

Convert bnxt to use new macros rather than open code the logic.
Two differences:
(1) bnxt_tx_int() will now only issue a memory barrier if it sees
    enough space on the ring to wake the queue. This should be fine,
    the mb() is between the writes to the ring pointers and checking
    queue state.
(2) we'll start the queue instead of waking on race, this should
    be safe inside the xmit handler.

Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>