Remove ext3 from petitboot kernel, use ext4 to mount ext3

This is, in fact, what was already going on behind the scenes.

This change saves 86kb in zImage.epapr:
-rwxr-xr-x 1 stewart users 13632614 Aug 18 11:10 zImage.epapr
-rwxr-xr-x 1 stewart users 13546598 Aug 18 11:18 zImage.epapr

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
diff --git a/openpower/configs/linux/skiroot_defconfig b/openpower/configs/linux/skiroot_defconfig
index c2572fd..0d02a46 100644
--- a/openpower/configs/linux/skiroot_defconfig
+++ b/openpower/configs/linux/skiroot_defconfig
@@ -177,9 +177,7 @@
 CONFIG_VIRTIO_PCI=y
 # CONFIG_IOMMU_SUPPORT is not set
 CONFIG_EXT2_FS=n
-CONFIG_EXT3_FS=y
-CONFIG_EXT3_FS_POSIX_ACL=y
-CONFIG_EXT3_FS_SECURITY=y
+CONFIG_EXT3_FS=n
 CONFIG_EXT4_FS=y
 CONFIG_EXT4_FS_POSIX_ACL=y
 CONFIG_EXT4_FS_SECURITY=y