libmodbus: upgrade 3.1.11 -> 3.1.12

Add 'tag' to SRC_URI

Changelog:
  https://github.com/stephane/libmodbus/releases/tag/v3.1.12

Changes:
- Fix FD_SET overflow when socket fd >= FD_SETSIZE.
- Check dest pointer not null and nb in read functions.
- NULL check for src and nb < 1 validation in write functions.
- modbus_reply: don't compute address for FC 0x07/0x11.
- Use O_NONBLOCK instead of deprecated O_NDELAY
- Explicit cast for Coverity CID 416366.
- Document required buffer size of modbus_receive.
- Document macros for error codes corresponding to Modbus exceptions
- Fix example of modbus_rtu_set_serial_mode
- Test filesystem provides symlink in autogen.sh
- Sync API signatures with the documentation.
- Many documentation fixes and typo corrections.
- Add coverage target and helper script.

Signed-off-by: Andrej Kozemcak <andrej.kozemcak@siemens.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-extended/libmodbus/libmodbus_3.1.12.bb

@@ -6,8 +6,8 @@ SECTION = "libs"
 LICENSE = "LGPL-2.1-or-later"
 LIC_FILES_CHKSUM = "file://COPYING.LESSER;md5=4fbd65380cdd255951079008b364516c"
 
-SRC_URI = "git://github.com/stephane/libmodbus;branch=master;protocol=https"
-SRCREV = "5190e5e141780ae481f24be16d7b39a5f3ad8f8f"
+SRC_URI = "git://github.com/stephane/libmodbus;branch=master;protocol=https;tag=v${PV}"
+SRCREV = "9af6c16074df566551bca0a7c37443e48f216289"
 
 
 inherit autotools pkgconfig