octeontx2-pf: add Support QSGMII mode

commit bfd6fb45c282b55ffccf54b5926c76f3b9e6e4cd from
git@git.assembla.com:cavium/WindRiver.linux.git

Update ethtool supported mode mask such that QSGMII port
will be visible in supported link modes.

Change-Id: If6a3f7da9b927201137dcb9ff26d94e09ba144ea
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/38067


Tested-by: sa_ip-sw-jenkins <sa_ip-sw-jenkins@marvell.com>
Reviewed-by: Sunil Kovvuri Goutham <Sunil.Goutham@cavium.com>
Signed-off-by: Ruiqiang Hao <Ruiqiang.Hao@windriver.com>