selftests: mlxsw: Set headroom size of correct port

selftests: mlxsw: Set headroom size of correct port

[ Upstream commit 2ff2c7e274392871bfdee00ff2adbb8ebae5d240 ]

The test was setting the headroom size of the wrong port. This was not
visible because of a firmware bug that canceled this bug.

Set the headroom size of the correct port, so that the test will pass
with both old and new firmware versions.

Fixes: bfa804784e32 ("selftests: mlxsw: Add a PFC test")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Link: https://lore.kernel.org/r/20201230114251.394009-1-idosch@idosch.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>