octeontx2-pf: Backport physical link status changes

commit 13b3fa727d7a5575f7bd04e26db813d771760dad from
git@git.assembla.com:cavium/WindRiver.linux.git

This patch consists of below changes
	 - Uses ethtool standard  APIs to display supported
	   and advertisied modes
	 - code optimization

Add linkmode.h which exposes linkmode APIs

Change-Id: Ibe26aeebef8c5b4c2f7d42dd12fbbf82a1b992ea
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/47406


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