Label goldfish block devices with their own types.

This assigns block device types as per device/generic/goldfish/fstab.goldfish.
Eliminates (permissive) avc:  denied messages for fsck.

Change-Id: Ia72bdfb16975f051548b6b2c0636e4f907295789
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>