tty: serial: ip22zilog: Fix section mispatch warning

ip22zilog_prepare() is now called by driver probe routine, so it
shouldn't be in the __init section any longer.

Fixes: 3fc36ae6abd2 ("tty: serial: ip22zilog: Use platform device for probing")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202604020945.c9jAvCPs-lkp@intel.com/
Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Link: https://patch.msgid.link/20260402102154.136620-1-tbogendoerfer@suse.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>