firmware: google: make coreboot driver's remove callback return void

All coreboot drivers return 0 unconditionally in their remove callback.
Also the device core ignores the return value of the struct
bus_type::remove(), so make the coreboot remove callback return void
instead of giving driver authors the illusion they could return an error
code here.

All drivers are adapted accordingly.

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Link: https://lore.kernel.org/r/20210126215339.706021-1-uwe@kleine-koenig.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>