net: dsa: mv88e6xxx: fix shift of FID bits in mv88e6250_g1_vtu_loadpurge()

The comment is correct, but the code ends up moving the bits four
places too far, into the VTUOp field.

Fixes: bec8e572 (net: dsa: mv88e6xxx: implement vtu_getnext and vtu_loadpurge for mv88e6250)
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/global1_vtu.c

@@ -444,7 +444,7 @@ int mv88e6250_g1_vtu_loadpurge(struct mv88e6xxx_chip *chip,
 		 * VTU DBNum[5:4] are located in VTU Operation 9:8
 		 */
 		op |= entry->fid & 0x000f;
-		op |= (entry->fid & 0x0030) << 8;
+		op |= (entry->fid & 0x0030) << 4;
 	}
 
 	return mv88e6xxx_g1_vtu_op(chip, op);