bnxt_en: Refactor completion ring free routine

bnxt_en: Refactor completion ring free routine

Add a wrapper routine to free L2 completion rings.  This will be
useful later in the series.

Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Signed-off-by: Somnath Kotur <somnath.kotur@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20250213011240.1640031-5-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>