Add sysfs rule for vibrator in system_server

Helps fix vibrator HAL open issue

avc: denied { write } for pid=907 comm="system_server" name="enable" dev="sysfs" ino=20423 scontext=u:r:system_server:s0 tcontext=u:object_r:sysfs_vibrator:s0 tclass=file permissive=0

Bug: 32209928
Bug: 32225232

Test: m, booted, tested keypad to make sure vibrator works
Change-Id: I4977c42b7fac0c9503be04b6520487f2d6cbc903