Answer
I am getting an error in dmesg "brcmfmac: brcmf_sdio_htclk: HT Avail timeout (1000000): clkctl 0x50"
when trying to start my Sterling-LWB5+ radio.
In general, this error occurs when you do not have a 32kHz external oscillator in your design or it is mis-configured. This is required for all of the LWB series radios.
Here is more information about the oscillator: