pcmcia: sa1100: Make sa11x0_drv_pcmcia_legacy_remove() return void

sa11x0_drv_pcmcia_legacy_remove() returns zero unconditionally. Letting it
return void instead makes it easier to see in the caller that there is no
error to handle.

This is a preparation for making platform remove callbacks return void.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>