grep: bump to version 3.1

Add license file hash.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/grep/grep.hash

@@ -1,2 +1,4 @@
 # Locally calculated after checking signature
-sha256 e2c81db5056e3e8c5995f0bb5d0d0e1cad1f6f45c3b2fc77b6e81435aed48ab5  grep-3.0.tar.xz
+# http://ftp.gnu.org/gnu/grep/grep-3.1.tar.xz.sig
+sha256 db625c7ab3bb3ee757b3926a5cfa8d9e1c3991ad24707a83dde8a5ef2bf7a07e  grep-3.1.tar.xz
+sha256 ca372a7d92560b1fa9f6d832b440e8bcd62d9adfa8870c98287deab66d98310e  COPYING

package/grep/grep.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-GREP_VERSION = 3.0
+GREP_VERSION = 3.1
 GREP_SITE = $(BR2_GNU_MIRROR)/grep
 GREP_SOURCE = grep-$(GREP_VERSION).tar.xz
 GREP_LICENSE = GPL-3.0+