Since commit fc7a6209 ("bus: Make remove callback return void")
forces bus_type::remove be void-returned, it doesn't make much sense
for any bus based driver implementing remove callbalk to return
non-void to its caller.

As such, change the remove function for ac97 based drivers to return
void.
Signed-off-by: Dawei Li <set_pte_at@outlook.com>
Link: https://lore.kernel.org/r/TYCP286MB2323A5AB1B2578EF4FA15DA7CAFB9@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COMSigned-off-by: Takashi Iwai <tiwai@suse.de>