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 pid=81 comm="kworker/3:1" name="mmc0"
dev="debugfs" ino=14362 scontext=u:r:kernel:s0
tcontext=u:object_r:debugfs_mmc:s0 tclass=dir permissive=0

CRs-Fixed: 2131488
Change-Id: I3bdcded04efbb59a6e5f643fce83ffb13ad7528c