A spade bit will be fine, as already explained. A caution: Somebody said they are grabby. They are. Very grabby.
Your drill has plenty of torque (turning power) so start slowly and enter the wood square to the surface. You should see a nice round even hole form as the bit enters. If not, just ease off a little and straighten up. Then continue into the wood. Advanced to medium power with the drill trigger and grip the drill with both hands. Get above it, if you can. Do not get the drill turning with more power than you can hold back if the bit grabs.
If you use only one hand to hold the drill, are turning at top speed, and the bit bites, you can break a wrist because the torque changes from turning the bit to turning the drill handle itself, to turning your wrist.
The risk of that is not high if you go slowly. Take your time and feed gently. All my scary talk is overly cautionary.
In no time you will have nice whole to mount your lamp. If you can put a pice of wood behind the planned hole, you can eliminate a lot of splintering there, on the back. If it’s out of sight, don’t worry about splintering.
Or drill the hole from one side until the center point makes a hole in the other side. Then drill from the other side using that hole the point made as a pilot hole.
That’s my two bits worth.