MIPS: ralink: Fix invalid assignment of SoC type

Commit 418d29c8

 ("MIPS: ralink: Unify SoC id handling") introduced
broken code. We obviously need to assign the value.

Signed-off-by: John Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11993/


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