net: dsa: mv88e6xxx: fix shift of FID bits in mv88e6185_g1_vtu_loadpurge()

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

Fixes: 11ea809f1a74 (net: dsa: mv88e6xxx: support 256 databases)
Signed-off-by: Rasmus Villemoes <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/dsa/mv88e6xxx/global1_vtu.c

···
 		 * VTU DBNum[7:4] are located in VTU Operation 11:8
 		 */
 		op |= entry->fid & 0x000f;
-		op |= (entry->fid & 0x00f0) << 8;
+		op |= (entry->fid & 0x00f0) << 4;
 	}
 
 	return mv88e6xxx_g1_vtu_op(chip, op);