bnxt_en: Modify TX ring indexing logic.

bnxt_en: Modify TX ring indexing logic.

Change the TX ring logic so that the index increments unbounded and
mask it only when needed.

Modify the existing macros so that the index is not masked.  Add a
new macro RING_TX() to mask it only when needed to get the index of
txr->tx_buf_ring[].

Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/r/20231120234405.194542-11-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>