rootdir: defer zram init to boot_complete

based off https://source.android.com/devices/tech/perf/boot-times

rootdir/init.mt6735.rc

@@ -80,7 +80,6 @@ on post-fs
     symlink /sdcard /storage/sdcard0
 
     write /sys/block/zram0/comp_algorithm lz4
-    swapon_all /fstab.swap
     write /proc/sys/vm/page-cluster 0
 
     # change owner
@@ -684,6 +683,8 @@ on property:ro.board.platform=mt6753
     write /sys/devices/system/cpu/cpufreq/interactive/hispeed_freq 1300000
 
 on property:sys.boot_completed=1
+    # defer zram init after boot_complete
+    swapon_all /fstab.swap
     # end boot time fs tune
     write /sys/block/mmcblk0/queue/read_ahead_kb 128
     write /sys/block/mmcblk0/queue/nr_requests 128