net: sfp: Add tx-fault workaround for Huawei MA5671A SFP ONT

As noted elsewhere, various GPON SFP modules exhibit non-standard
TX-fault behaviour. In the tested case, the Huawei MA5671A, when used
in combination with a Marvell mv88e6085 switch, was found to
persistently assert TX-fault, resulting in the module being disabled.

This patch adds a quirk to ignore the SFP_F_TX_FAULT state, allowing the
module to function.

Change from v1: removal of erroneous return statment (Andrew Lunn)

Signed-off-by: Matthew Hagan <mnhagan88@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20220502223315.1973376-1-mnhagan88@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>