brcmfmac: correct error handling in brcmf_fws_init()

In brcmf_fws_init() the error flows were not properly handled
and the caller ignored the return value. The only action that
is allowed to fail in brcmf_fws_init() is setting the tlv in
firmware as the feature is not supported on all devices.

Cc: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>