allow recovery FUNCTIONFS_ENDPOINT_DESC

Commit ebc3a1a3 ("Move to ioctl
whitelisting for plain files / directories", Oct 10th), enabled ioctl
filtering on all files, including functionfs files. However, recovery
performs the ioctl FUNCTIONFS_ENDPOINT_DESC on functionfs files, so
allow it.

Addresses the following denial:

  audit: type=1400 audit(673009.476:507811): avc:  denied  { ioctl } for  pid=731 comm="recovery" path="/dev/usb-ffs/adb/ep1" dev="functionfs" ino=473 ioctlcmd=0x6782 scontext=u:r:recovery:s0 tcontext=u:object_r:functionfs:s0 tclass=file permissive=1

Test: policy compiles.
Bug: 119877813
Change-Id: I09715acc16ab319b8d8b1f233cefaec23a358962

public/recovery.te

@@ -76,6 +76,7 @@ recovery_only(`
   # Access /dev/usb-ffs/adb/ep0
   allow recovery functionfs:dir search;
   allow recovery functionfs:file rw_file_perms;
+  allowxperm recovery functionfs:file ioctl FUNCTIONFS_ENDPOINT_DESC;
 
   # Access to /sys/fs/selinux/policyvers for compatibility check
   allow recovery selinuxfs:file r_file_perms;