fstab: Specify discard option when mounting /cache.

Bug: 28347095
Change-Id: Ia13145281d2dd213b9c4d92f82763f659a0c4745
diff --git a/fstab.flounder b/fstab.flounder
index 54f948f..b6141ba 100644
--- a/fstab.flounder
+++ b/fstab.flounder
@@ -5,7 +5,7 @@
 
 /dev/block/platform/sdhci-tegra.3/by-name/APP   /system             ext4      ro                                                    wait,verify=/dev/block/platform/sdhci-tegra.3/by-name/MD1
 /dev/block/platform/sdhci-tegra.3/by-name/VNR   /vendor             ext4      ro                                                    wait,verify=/dev/block/platform/sdhci-tegra.3/by-name/MD1
-/dev/block/platform/sdhci-tegra.3/by-name/CAC   /cache              ext4      noatime,nosuid,nodev,nomblk_io_submit,errors=panic    wait,check
+/dev/block/platform/sdhci-tegra.3/by-name/CAC   /cache              ext4      noatime,nosuid,nodev,nomblk_io_submit,discard,errors=panic    wait,check
 /dev/block/platform/sdhci-tegra.3/by-name/UDA   /data               f2fs      noatime,nosuid,nodev,errors=recover    wait,check,forceencrypt=/dev/block/platform/sdhci-tegra.3/by-name/MD1
 /dev/block/platform/sdhci-tegra.3/by-name/UDA   /data               ext4      noatime,nosuid,nodev,nomblk_io_submit,errors=panic    wait,check,forceencrypt=/dev/block/platform/sdhci-tegra.3/by-name/MD1
 /dev/block/platform/sdhci-tegra.3/by-name/LNX   /boot               emmc      defaults                                              defaults