bnxt_en: Refactor TX ring allocation logic

Add a new bnxt_hwrm_tx_ring_alloc() function to handle allocating
a transmit ring.  This will be useful later in the series.

Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20250213011240.1640031-4-michael.chan@broadcom.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>