sepolicy : Allow kernel to search debugfs_mmc dir

Debugfs is failed to be initialized because of the denial below.
Add selinux policy to fix it.
avc: denied { search } for comm="kworker/0:1" name="mmc0"
dev="debugfs" ino=6562 scontext=u:r:kernel:s0
tcontext=u:object_r:debugfs_mmc:s0 tclass=dir permissive=0

CRs-Fixed: 2636489
Change-Id: I831a363d448b3efe11960c3937b04dbca80d37f3