ath79: improve factory.bin for some Senao devices

ath79: improve factory.bin for some Senao devices

Some boards with firmware made with Senao SDK based on Linux 3.3
have the following lines in the OEM upgrade script at
/etc/fwupgrade.sh

	local append=""
	local CONF_TAR="/tmp/sysupgrade.tgz"
	[ -f "$CONF_TAR" ] && append="-j $CONF_TAR"

and

	\# check FWINFO filename
	[ -z $(ls FWINFO* | grep -i ${modelname}) ] && errcode="1"

This addition also prevents needing to factory reset after flashing
for some boards that also have these lines in the script

	\# Support downgrade but do default (Smart v2.x.x.x -> senaowrt v1.x.x.x)
	[ $(ls FWINFO* | grep -i ${modelname} | cut -d "-" -f4 | cut -c 2) -lt 2 ] && append=""

Signed-off-by: Michael Pratt <mcpratt@pm.me>