Delete sysfs_writable from core policy.

It's only used by the emulators, never by core policy.
Move the definition to the emulators.

Bug: 28221393
Change-Id: I7ca56e04d611cfccde507313ba9c2a0a71d54d06

file.te

@@ -23,7 +23,6 @@ type selinuxfs, fs_type, mlstrustedobject;
 type cgroup, fs_type, mlstrustedobject;
 type sysfs, fs_type, sysfs_type, mlstrustedobject;
 type sysfs_uio, sysfs_type, fs_type;
-type sysfs_writable, fs_type, sysfs_type, mlstrustedobject;
 type sysfs_batteryinfo, fs_type, sysfs_type;
 type sysfs_bluetooth_writable, fs_type, sysfs_type, mlstrustedobject;
 type sysfs_hwrandom, fs_type, sysfs_type;