oxnas: move service file to correct place

This service file has been misplaced from the very beginning.

Fixes: dcc34574efba ("oxnas: bring in new oxnas target")
Signed-off-by: Sungbo Eo <mans0n@gorani.run>
(cherry picked from commit 01961f163d927d6b44097f48a67bbc5b4c63eaf7)

diff --git a/target/linux/oxnas/base-files/init.d/set-irq-affinity b/target/linux/oxnas/base-files/etc/init.d/set-irq-affinity
similarity index 100%
rename from target/linux/oxnas/base-files/init.d/set-irq-affinity
rename to target/linux/oxnas/base-files/etc/init.d/set-irq-affinity