brcmfmac: pcie/sdio/usb: Get CLM blob via standard firmware mechanism

brcmfmac: pcie/sdio/usb: Get CLM blob via standard firmware mechanism

Now that the firmware fetcher can handle per-board CLM files, load the
CLM blob alongside the other firmware files and change the bus API to
just return the existing blob, instead of fetching the filename.

This enables per-board CLM blobs, which are required on Apple platforms.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Hector Martin <marcan@marcan.st>