MIPS: Alchemy: irq code and constant cleanup

replace au_readl/au_writel with __raw_readl/__raw_writel,
and clean up IC-related stuff from the headers.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
To: Linux-MIPS <linux-mips@linux-mips.org>
Cc: Florian Fainelli <florian@openwrt.org>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Patchwork: https://patchwork.linux-mips.org/patch/2354/


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