Add first firmware for the Mellanox Spectrum switch, as a followup to the
recently added commit:
6b7421992b8d ("mlxsw: spectrum: Validate firmware revision on init")

The version of the firmware release is 13.1420.122
Signed-off-by: Yotam Gigi <yotamg@mellanox.com>
Signed-off-by: Kyle McMartin <kyle@kernel.org>