MIPS: BCM47XX: Get rid of calls to KSEG1ADDR

We should be using ioremap_nocache helper which handles remaps in a
smarter way.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: http://patchwork.linux-mips.org/patch/7611/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>