sgdisk: allow BLKRRPART

Allow sgdisk to force the kernel to re-read the partition table.

Addresses the following denial:

avc: denied { ioctl } for path=/dev/block/vold/disk:7,0 dev=tmpfs ino=710640 ioctlcmd=125f scontext=u:r:sgdisk:s0 tcontext=u:object_r:vold_device:s0 tclass=blk_file permissive=0

Bug: 118890056
Test: policy compiles
Test:
  1) adb shell sm set-force-adoptable on
  2) adb shell sm set-virtual-disk true
  3) On device, pick the drop-down notification and
     choose "use as phone/internal storage" to adopt the virtual SD card.
Change-Id: I6825cf526cc48aa2a17afab14eadb6134bfc56f9