hikey960: fstab.hikey960: Set metadata as first_stage_mount to resolve adb remount overlay persistence issues

It was reported that changes made after "adb remount" were not
persisting after a reboot. After reproducing and debugging, I
was at a bit of a loss for why.

After quite a bit of floundering around, I finally realized we
were missing first_stage_mount from the fstab arguments. This
prevents the metadata partition from being available early
enough for the overlay images to be located and applied at
bootup.

Signed-off-by: John Stultz <john.stultz@linaro.org>
Change-Id: I63a8cedacbace33cceee7f83121a4b83dd996cc3
diff --git a/hikey960/fstab.hikey960 b/hikey960/fstab.hikey960
index fe43486..5891323 100644
--- a/hikey960/fstab.hikey960
+++ b/hikey960/fstab.hikey960
@@ -7,7 +7,7 @@
 #/dev/block/platform/soc/ff3b0000.ufs/by-name/cache       /cache     ext4    discard,noauto_da_alloc,data=ordered,user_xattr,barrier=1    wait
 #/dev/block/platform/soc/ff3b0000.ufs/by-name/userdata    /data      ext4    discard,noauto_da_alloc,data=ordered,user_xattr,barrier=1    wait
 /dev/block/by-name/userdata    /data      ext4    discard,noatime,nosuid,nodev,noauto_da_alloc,data=ordered,user_xattr,barrier=1,inlinecrypt    wait,formattable,fileencryption=aes-256-xts:aes-256-cts:v2+inlinecrypt_optimized,quota
-/dev/block/by-name/cache	/metadata       ext4    noatime,nosuid,nodev,discard                                    wait,formattable
+/dev/block/by-name/cache	/metadata       ext4    noatime,nosuid,nodev,discard     wait,formattable,first_stage_mount,check
 /devices/platform/soc/ff37f000.dwmmc1/mmc_host/mmc*      auto       auto    defaults    voldmanaged=sdcard1:auto,encryptable=userdata
 /devices/platform/soc/ff200000.hisi_usb/ff100000.dwc3/xhci-hcd.*.auto/usb*               auto               auto      defaults  voldmanaged=usbdisk:auto,encryptable=userdata
 /devices/platform/soc/f4000000.pcie/pci0000:00/0000:00:00.0/0000:01:00.0/nvme/nvme*      auto       auto    defaults    voldmanaged=nvmedisk:auto,encryptable=userdata