MIPS: Lantiq: Reorganize xway code

MIPS: Lantiq: Reorganize xway code

Inside the folder arch/mips/lantiq/xway, there were alot of small files
with lots of duplicated code. This patch adds a wrapper function for
inserting and requesting resources and unifies the small files into one
bigger file.

This patch makes the xway code consistent with the falcon support added
later in this series.

Signed-off-by: John Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3270/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>