tty: hvc-iucv: fix function pointer casts

tty: hvc-iucv: fix function pointer casts

clang warns about explicitly casting between incompatible function
pointers:

drivers/tty/hvc/hvc_iucv.c:1100:23: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
 1100 |         priv->dev->release = (void (*)(struct device *)) kfree;
      |                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Add a separate function to handle this correctly.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20240213101756.461701-1-arnd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>