Merge branch 'net-phylink-fix-pcs-without-autoneg'

Russell King says:

====================
net: phylink: fix PCS without autoneg

Eric Woudstra reported that a PCS attached using 2500base-X does not
see link when phylink is using in-band mode, but autoneg is disabled,
despite there being a valid 2500base-X signal being received. We have
these settings:

	act_link_an_mode = MLO_AN_INBAND
	pcs_neg_mode = PHYLINK_PCS_NEG_INBAND_DISABLED

Eric diagnosed it to phylink_decode_c37_word() setting state->link
false because the full-duplex bit isn't set in the non-existent link
partner advertisement word (which doesn't exist because in-band
autoneg is disabled!)

The test in phylink_mii_c22_pcs_decode_state() is supposed to catch
this state, but since we converted PCS to use neg_mode, testing the
Autoneg in the local advertisement is no longer sufficient - we need
to be looking at the neg_mode, which currently isn't provided.

We need to provide this via the .pcs_get_state() method, and this
will require modifying all PCS implementations to add the extra
argument to this method.

Patch 1 uses the PCS neg_mode in phylink_mac_pcs_get_state() to correct
the now obsolute usage of the Autoneg bit in the advertisement.

Patch 2 passes neg_mode into the .pcs_get_state() method, and updates
all users.

Patch 3 adds neg_mode as an argument to the various clause 22 state
decoder functions in phylink, modifying drivers to pass the neg_mode
through.

Patch 4 makes use of phylink_mii_c22_pcs_decode_state() rather than
using the Autoneg bit in the advertising field.

Patch 5 may be required for Eric's case - it ensures that we report
the correct state for interface types that we support only one set
of modes for when autoneg is disabled.
====================

Link: https://patch.msgid.link/Z4TbR93B-X8A8iHe@shell.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>