brcmfmac: do not convert linux error to firmware error string

In case of a linux error brcmf_fil_cmd_data() blurts an error message
in which the error code is translated to an error string. However, it
maps it to a firmware error string which should not happen. Simply
print only the numeric error code and be done with it.

Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>