patches/openwrt: 5.15: fix support for HALNy GPON SFP

While rebasing this patch series, I forgot to add one more change in the
last patch, which should be now fixed. It was missing the changes in
sfp.c file as there was only included fix for this GPON SFP module, but
there was no added support for it, actually. :-(

Fixes 3cd00f59 ("patches/openwrt: 5.15: add support for HALny GPON SFP
")