Revert "MIPS: kernel: {ftrace,kgdb}: Set correct address limit for cache flushes"

Revert "MIPS: kernel: {ftrace,kgdb}: Set correct address limit for cache flushes"

This reverts commit 5fd2ebfc61304ebb2f8b31c32a2fcdd18b56e1d5.

All icache flushes in this code paths are done via flush_icache_range(),
which only uses normal cache instruction. And this is the correct thing
for EVA mode, too. So no need to do set_fs(KERNEL_DS) here.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>