Fixes for some filepath errors with 32-bit builds

[rcswift]

I'm trying to build a kernel-rt for a PiZero and I ran into the same errors mentioned in #16 and #14. These two changes seem to allow the build to complete and result in a valid image.

From the docs:

Next, build the kernel. This step can take a long time, depending on your Raspberry Pi model.

• Run the following commands to build a 64-bit kernel: make -j6 Image.gz modules dtbs
• Run the following command to build a 32-bit kernel: make -j6 zImage modules dtbs

2. Depending on your kernel version, run the following command:

• For kernels up to version 6.4: sudo cp arch/arm/boot/dts/*.dtb /boot/firmware/
• For kernels version 6.5 and above: sudo cp arch/arm/boot/dts/broadcom/*.dtb /boot/firmware/