Acting on a tip, I made the two changes in this commit: linux-firmware: Update to version 20220509 to my Makefile and rebuilt OpenWrt.
However, I still get the same error messages in my system log and the QCA6174 WiFi adapter is not functional. Issue opened.
After a bit of debugging in the kernel module, I found that the source of the error was due to this function call dma_alloc_coherent failing to return a valid address. After searching for a solution to that issue, I found this: DMA memory within 32-bit address space on RPI4 (CM4)
The solution is to add
dtoverlay=pcie-32bit-dma
to /boot/config.txt on the RPi CM4.
Better yet, for OpenWrt you can add it to the config file located here: <buildroot>/target/linux/bcm27xx/image/config.txt and it will always be in your build.