[202012][kernel][swss]: Linux kernel and SWSS submodule update (#11929)

Include following new kernel commits:
- 815cb34 [patch]: Add accept_untracked_na kernel param (#291)
- fbb76cc Remove kernel config SERIAL_8250_RUNTIME_UARTS (#286)

Introduce following SWSS commits:
- eedf59d [intfmgr]: Enable `accept_untracked_na` kernel param (#2439)
- bbd4eb7 [BFD]Clean up state_db BFD entries on swss restart (#2434) (#2435)
- aa7b546 [FDB] [202012] Fix fbdorch to properly handle syncd FDB FLUSH Notif (#2401)
- 4190c13 Support for platforms based on Clounix Networks' device (#2399)

Signed-off-by: Lawrence Lee <lawlee@microsoft.com>