staging: r8712u: Fix driver to support ad-hoc mode

Driver r8712u is unable to handle ad-hoc mode. The issue is that when
the driver first starts, there will not be an SSID for association.
The fix is to always call the "select and join from scan" routine when
in ad-hoc mode.

Note: Ad-hoc mode worked intermittently before. If the driver had
previously been associated, then things were OK.

Signed-off-by: Jeff Chua <jeff.chua.linux@gmail.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>