goldfish: Fix /cache partition type.

Starting with kernel 3.10, yaffs2 partitions are no longer
supported. This patch changes the type of the cache partition
image to 'ext4' to allow booting a system based on such kernel,
for example aosp_x86_64-userdebug.

This works after the following patch was applied to the emulator:

    https://android-review.googlesource.com/#/c/98204/

Note that this works properly because the platform build system
will extract the value to know how to generate cache.img at build
time properly.

  See $AOSP/build/tools/releasetools/img_from_target_files

BUG=15144004

Change-Id: I6c123c9baf84d13507a44b8205ec79746fb2628f
diff --git a/fstab.goldfish b/fstab.goldfish
index be83a16..0a67f1d 100644
--- a/fstab.goldfish
+++ b/fstab.goldfish
@@ -4,6 +4,5 @@
 # specify MF_CHECK, and must come before any filesystems that do specify MF_CHECK
 /dev/block/mtdblock0                                    /system             ext4      ro,barrier=1                                         wait
 /dev/block/mtdblock1                                    /data               ext4      noatime,nosuid,nodev,barrier=1,nomblk_io_submit      wait,check
-# 2014-03-13: Yes. yaffs2. The emulator tools need some updating to support ext4 for the cache image.
-/dev/block/mtdblock2                                    /cache              yaffs2      noatime,nosuid,nodev  wait,check
+/dev/block/mtdblock2                                    /cache              ext4      noatime,nosuid,nodev  wait,check
 /devices/platform/goldfish_mmc.0                        auto                vfat      defaults                                             voldmanaged=sdcard:auto