package/libmodbus: bump to version 3.1.8

Switch site to get latest release

https://github.com/stephane/libmodbus/releases/tag/v3.1.8

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/libmodbus/libmodbus.hash

@@ -1,3 +1,3 @@
 # Locally computed
-sha256  7dfe958431d0570b271e1a5b329b76a658e89c614cf119eb5aadb725c87f8fbd  libmodbus-3.1.7.tar.gz
+sha256  b122f2bc29f749702a22c0a760a7ca2182d541f5fa26bf25e3431f907b606f3c  libmodbus-3.1.8.tar.gz
 sha256  dc626520dcd53a22f727af3ee42c770e56c97a64fe3adb063799d8ab032fe551  COPYING.LESSER

package/libmodbus/libmodbus.mk

@@ -4,8 +4,8 @@
 #
 ################################################################################
 
-LIBMODBUS_VERSION = 3.1.7
-LIBMODBUS_SITE = http://libmodbus.org/releases
+LIBMODBUS_VERSION = 3.1.8
+LIBMODBUS_SITE = https://github.com/stephane/libmodbus/releases/download/v$(LIBMODBUS_VERSION)
 LIBMODBUS_LICENSE = LGPL-2.1+
 LIBMODBUS_LICENSE_FILES = COPYING.LESSER
 LIBMODBUS_CPE_ID_VENDOR = libmodbus