Remove internal LoopConfig struct

The struct is now part of golang.org/x/sys.
Follow-up for containerd#9805

Signed-off-by: Alexandru Matei <[email protected]>

Author: alex-matei

core/mount/losetup_linux.go

@@ -35,13 +35,6 @@ const (
 	ebusyString = "device or resource busy"
 )
 
-type LoopConfig struct {
-	Fd        uint32
-	BlockSize uint32
-	Info      unix.LoopInfo64
-	Reserved  [8]uint64
-}
-
 // LoopParams parameters to control loop device setup
 type LoopParams struct {
 	// Loop device should forbid write