Sync c-tx39.c with c-r4k.c.

    
tx39_flush_cache_range() does nothing if !cpu_has_dc_aliases.  It should
flush d-cache and invalidate i-cache since the TX39(H2) has separate I/D
cache.
    
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>