[barefoot][platform][arista] Add sfp_type to Sfp class objects

[vboykox]

Fixes:

Traceback (most recent call last):
  File "/usr/bin/xcvrd", line 1208, in <module>
    main()
  File "/usr/bin/xcvrd", line 1205, in main
    xcvrd.run()
  File "/usr/bin/xcvrd", line 1166, in run
    self.init()
  File "/usr/bin/xcvrd", line 1145, in init
    post_port_sfp_dom_info_to_db(is_warm_start, self.stop_event)
  File "/usr/bin/xcvrd", line 432, in post_port_sfp_dom_info_to_db
    post_port_dom_info_to_db(logical_port_name, dom_tbl, stop_event)
  File "/usr/bin/xcvrd", line 357, in post_port_dom_info_to_db
    if platform_chassis.get_sfp(physical_port).sfp_type == 'QSFP_DD':
AttributeError: 'Sfp' object has no attribute 'sfp_type'

Environment
SONiC Software Version: SONiC.HEAD.729-dirty-20200727.195955
Distribution: Debian 10.4
Kernel: 4.19.0-9-2-amd64
Build commit: 89184038

[vboykox]

@akokhan

[vboykox]

@tsuna @aaronbee @pooya @peadar

[vboykox]

@Staphylo

[Staphylo]

Thanks for the PR.
It can't merge via github as it has to go through our internal process first.
I'll be back on Tuesday to see to it if @zzhiyuan doesn't cherry-pick it by then.

[Staphylo]

I cherry-picked your change and it's now running some tests. I believe it should go well.
Your change will motivate an upstreaming session in the coming days.
I will resolve/close this issue once it's done.

[Staphylo]

Merged via 99e5e07