MIPS: Remove MIPS4K_ICACHE_REFILL_WAR and MIPS_CACHE_SYNC_WAR

Neither MIPS4K_ICACHE_REFILL_WAR nor MIPS_CACHE_SYNC_WAR are implemented,
so removing defines for it won't change anything.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>