net/bnxt: cleanup comments

net/bnxt: cleanup comments

- updated one comment for more readability and understanding
- fixed typo in comments
- moved a comment to right place
- removed one out-of-date comment
- removed few commented code

Fixes: f2a768d4d186 ("net/bnxt: add completion ring")
Cc: stable@dpdk.org
Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>