doc: update release notes for bnxt

doc: update release notes for bnxt

Update release doc briefly describing updates to bnxt PMD for
19.11 release.

The support for these was added in the following commits:
1) b150a7e7ee66 ("net/bnxt: support LRO on Thor adapters")
2) be14720def9c ("net/bnxt: support FW reset")
3) df6cd7c1f73a ("net/bnxt: handle reset notify async event from FW")
4) 698aa7e95325 ("net/bnxt: add code to determine the Tx COS queue")
5) 04102f2ffc8c ("net/bnxt: update HWRM API to version 1.10.1.6")

Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>