bnxt_en: Add coalescing setup for 57500 chips.

On legacy chips, the CP ring may be shared between RX and TX and so only
setup the RX coalescing parameters in such a case.  On 57500 chips, we
always have a dedicated CP ring for TX so we can always set up the
TX coalescing parameters in bnxt_hwrm_set_coal().

Also, the min_timer coalescing parameter applies to the NQ on the new
chips and a separate firmware call needs to be made to set it up.

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