init: qcom: Set ro.hw.nav_keys property for 8974 liquid

MSM8974 Liquid device do not have hardware navigation keys.
Set property ro.hw.nav_keys to 0 to enable Android sw
navigation bar.

Change-Id: I1dd00dcf4c87727d1c92cc9daf77dd238b35c59b

rootdir/etc/init.qcom.early_boot.sh

@@ -107,6 +107,9 @@ case "$1" in
         case "$soc_hwplatform" in
             "Liquid")
                 setprop ro.sf.lcd_density 160
+                # Liquid do not have hardware navigation keys, so enable
+                # Android sw navigation bar
+                setprop ro.hw.nav_keys 0
                 ;;
             *)
                 setprop ro.sf.lcd_density 320