brcmfmac: fix firmware request processing if nvram load fails

When nvram loading fails a double free occurred. Fix this and reorg the
code a little.

Fixes: d09ae51a ("brcmfmac: pass struct in brcmf_fw_get_firmwares()")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>