lmkd: grant read access to all of /sys

avc: denied { search } for pid=394 comm="lmkd" name="lowmemorykiller" dev="sysfs" ino=7541 scontext=u:r:lmkd:s0 tcontext=u:object_r:sysfs_lowmemorykiller:s0 tclass=dir permissive=0

Bug: 29558514
Change-Id: Iaae907a92976af2a9dcb58be5643b8614dcde174

lmkd.te

@@ -20,6 +20,7 @@ r_dir_file(lmkd, system_server)
 allow lmkd system_server:file write;
 
 ## Writes to /sys/module/lowmemorykiller/parameters/minfree
+r_dir_file(lmkd, sysfs_type)
 allow lmkd sysfs_lowmemorykiller:file w_file_perms;
 
 # Send kill signals