wpa-supplicant: don't break the DBus service file

wpa-supplicant: don't break the DBus service file

The recipe exports $BINDIR as ${sbindir} and the build system uses this when
writing the DBus service file, so sedding it and replacing $base_sbindir with
$sbindir (/sbin and /usr/sbin) isn't useful when it ends up as
/usr/usr/sbin/wpa_supplicant.

[YOCTO: #3202]

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>