MIPS: lantiq: Move macro directly to iomem function

Using the variable as a temporary holder for the macro of the register
offset value is not necessary. Move it directly to the IOMEM read/write
call.

Signed-off-by: Petr Cvek <petrcvekcz@gmail.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: hauke@hauke-m.de
Cc: john@phrozen.org
Cc: linux-mips@vger.kernel.org
Cc: openwrt-devel@lists.openwrt.org
Cc: pakahmar@hotmail.com