brcmfmac: simplify if-else condition in brcmf_cfg80211_escan()

Code flow was:
	err = foo();
	if (!err)
		return err;
	else
		goto exit;
	return 0;

Changed it to just to exit label if err is non-zero.

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: Franky Lin <frankyl@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>