rtlwifi: squash warning in _usb_read_sync

drivers/net/wireless/rtlwifi/usb.c: In function ‘_usb_read_sync’:
drivers/net/wireless/rtlwifi/usb.c:102:6: warning: ‘status’ may be used uninitialized in this function
drivers/net/wireless/rtlwifi/usb.c:102:6: note: ‘status’ was declared here

My compiler is dumb, but better to eliminate the warning than to have
anyone waste time evaluating this again...

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>