MIPS: Fix CDMM to use native endian MMIO reads

The MIPS Common Device Memory Map (CDMM) is internal to the core and has
native endianness. There is therefore no need to byte swap the accesses
on big endian targets, so convert the CDMM bus driver to use
__raw_readl() rather than readl().

Fixes: 8286ae03

 ("MIPS: Add CDMM bus support")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9904/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>