SPDX: Add ISC SPDX-License-Identifier

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Wolfgang Denk <wd@denx.de>

Licenses/README

@@ -66,3 +66,4 @@ BSD 2-Clause License				BSD-2-Clause	Y		bsd-2-clause.txt	http://spdx.org/license
 BSD 3-clause "New" or "Revised" License		BSD-3-Clause	Y		bsd-3-clause.txt	http://spdx.org/licenses/BSD-3-Clause#licenseText
 IBM PIBS (PowerPC Initialization and		IBM-pibs			ibm-pibs.txt
 	Boot Software) license
+ISC License					ISC		Y		isc.txt			https://spdx.org/licenses/ISC

Licenses/isc.txt

+ISC License:
+Copyright (c) 2004-2010 by Internet Systems Consortium, Inc. ("ISC")
+Copyright (c) 1995-2003 by Internet Software Consortium
+
+Permission to use, copy, modify, and/or distribute this software
+for any purpose with or without fee is hereby granted,
+provided that the above copyright notice and this permission notice
+appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE
+FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR
+ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+THIS SOFTWARE.