scripts/qemustart: use squashfs instead of ext4

The qemustart script currently picks the ext4 filesystem rather than
squashfs, while the latter is default for nearly all OpenWrt targets.

Change the default behaviour of qemustart to be in line with the rest.

Signed-off-by: Paul Spooren <mail@aparcar.org>

scripts/qemustart

@@ -257,7 +257,7 @@ start_qemu_x86() {
 	local mach="${o_mach:-pc}"
 
 	[ -n "$rootfs" ] || {
-		rootfs="$o_bindir/openwrt-$o_target-${o_subtarget%-*}-generic-ext4-combined.img"
+		rootfs="$o_bindir/openwrt-$o_target-${o_subtarget%-*}-generic-squashfs-combined.img"
 		if [ ! -f "$rootfs" -a -s "$rootfs.gz" ]; then
 			gunzip "$rootfs.gz"
 		fi