The unregister_prom_console() has been removed since
commit 36a88530 ("[MIPS] Fix and cleanup the mess that a dozen
prom_printf variants are."), so remove it.
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Acked-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>