wpa-supplicant: add wpa_supplicant.conf to CONFFILES and don't install it twice

wpa-supplicant: add wpa_supplicant.conf to CONFFILES and don't install it twice

* first we install ${WORKDIR}/wpa_supplicant.conf-sane
  install -m 600 ${WORKDIR}/wpa_supplicant.conf-sane ${D}${sysconfdir}/wpa_supplicant.conf
  and a bit later in do_install we were overwritting it with ${WORKDIR}/wpa_supplicant.conf
  install -m 644 ${WORKDIR}/wpa_supplicant.conf ${D}${sysconfdir}
* notice that this patch also changes .conf permissions from 644 back to 600

(From OE-Core rev: 583fdb62c73851b439bdf0c8e50f74073e566d5a)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>