brcmfmac: print firmware reported general status errors

Firmware may report general errors using a special message type. Add
basic support for it by simply decoding & printing an error number.

A sample situation in which firmware reports a buf error:
CONSOLE: 027084.733 no host response IOCTL buffer available..so fail the request
will now produce a "Firmware reported general error: 9" on the host.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>