Keep pre-existing sysfs write permissions.

Commit: b144ebab added the sysfs_usb
type and granted the read perms globally, but did not add write
permissions for all domains that previously had them.  Add the ability
to write to sysfs_usb for all domains that had the ability to write to
those files previously (sysfs).

Address denials such as:
type=1400 audit(1904.070:4): avc:  denied  { write } for  pid=321 comm="ueventd" name="uevent" dev="sysfs" ino=1742 scontext=u:r:ueventd:s0 tcontext=u:object_r:sysfs_usb:s0 tclass=file permissive=0

Bug: 28417852
Change-Id: I4562ea73f2158ebefba74b58ca572f2176d1b849