This is actually a problem I had to deal with way in the begging of
ARM64. What was done in the github tree was to have the one of the DTS
files(in this case 64) #include the 32 bit dts. That way it's not
needed to have the symbolic link and install should work.
I know it's ulgy, but it works...
Take a look at:
https://github.com/raspberrypi/linux/blob/rpi-4.10.y/arch/arm64/boot/dt
s/broadcom/bcm2710-rpi-3-b.dts
Here is what the file contains:
#define RPI364
#include "../../../../arm/boot/dts/bcm2710-rpi-3-b.dts"