brcmfmac: fix brcmf_wiphy_wowl_params() NULL pointer dereference

The kernel BUG happens when wowl is enabled from firmware. In
brcmf_wiphy_wowl_params(), cfg is a NULL pointer because it is
drvr->config returned from wiphy_to_cfg(), and drvr->config is not set
yet. To fix it, set drvr->config before brcmf_setup_wiphy() which
calls brcmf_wiphy_wowl_params().

Fixes: 856d5a01 ("brcmfmac: allocate struct brcmf_pub instance using wiphy_new()")
Signed-off-by: Winnie Chang <winnie.chang@cypress.com>
Signed-off-by: Chi-Hsien Lin <chi-hsien.lin@cypress.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>