staging: fbtft: Make fbtft_remove_common() return void

staging: fbtft: Make fbtft_remove_common() return void

fbtft_remove_common() is only called with a non-NULL fb_info. (All
callers are in remove callbacks and the matching probe callbacks set
driver data accordingly.) So fbtft_remove_common() always returns zero.
Make it return void instead which makes it easier to see in the callers
that there is no error to handle.

Also the return value of platform and spi remove callbacks is ignored
anyway and not freeing resources in .remove() is a bad idea.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20211012153945.2651412-20-u.kleine-koenig@pengutronix.de
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>