The GPIO node is called &tlmm for ipq401x, also you could use compatible = "gpio-keys";
(interrupt-based) instead of gpio-keys-polled, and thus remove the poll-interval.
The keys node would go after soc , i.e. insert between lines 232-233.
Did you verifiy which gpio pin is actually connected to the reset button, or are you just trying to add your own reset button to a different gpio? (It looks like there is a tactile switch on the board next to the power connector, but there is currently no reset gpio definition in the Wallytech dts at all...)
There is a reset button on the board the one you mention next to the power plug.
I don't have any developer documentation but I think it is gpio 29, but I have contact with the dev at Wally's I can confirm this.
The board comes with qsdk openwrt but the dev said that some use it as a sim card switch so it is unasigned currently.
I saw an include in another device I can add that also.