Add support for dlink DIR-878 R1

Thx for your reply @Lucky1

I have added a PR:

So it sounds like I should have used the dlink fw_update tool to push a russian dlink fw and that would run over the bootloader with a version that doesnt check for sigantures...
Any way to revert to stock and retry? I have saved all the flash partitions prior to switching to opewrt.

My setup is working well now with openwrt so not sure I will try that but want to have some backup plan if openwrt gets corrupted from some reason..

On the router box it says:
H/W ver: R1 F/W ver: 1.0.0
UPC Code /IL/R1B