meta-facebook: add emmc dependencies and timeout

Add dependencies so that the `emmc-init` service only runs if the
device is present.  Add a timeout parameter to the fstab entry
for the device so that the timeout is a reasonably short amount,
since we expect the device to always be immediately available.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I405a6773ff71f9eb047c4bb9d684fdd9b5d97948
diff --git a/meta-facebook/recipes-fb/emmc-init/files/emmc-init.service b/meta-facebook/recipes-fb/emmc-init/files/emmc-init.service
index 1a5ddcf..f093f3d 100644
--- a/meta-facebook/recipes-fb/emmc-init/files/emmc-init.service
+++ b/meta-facebook/recipes-fb/emmc-init/files/emmc-init.service
@@ -1,6 +1,8 @@
 [Unit]
 Description=eMMC initialize check
 Before=mnt-data.mount
+Requires=dev-mmcblk0.device
+After=dev-mmcblk0.device
 
 [Service]
 ExecStart=/usr/libexec/emmc-init/emmc-init