[MIPS] IP22: Fix crashes due to wrong L1_CACHE_BYTES

The introduction of a real dma cache invalidate makes it important
to have a correct cache line size, otherwise the kernel will gives
out two memory segment, which might share one cache line. The R4400
Indy/Indigo2 CPU modules are using a second level cache line size
of 128 bytes, so MIPS_L1_CACHE_SHIFT needs to be bumped up to 7 for
IP22.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>