MIPS: IP28: Select correct L1_CACHE_SHIFT

IP28 has 128 byte cache lines.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7548/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>