sysrepo: Use correct SPDX License Identifier

[BKPepe]

Maintainer: @mislavn
Compile tested: Turris Omnia, mvebu (cortex-a9), OpenWrt master
Run tested: N/A

Description:

• Add PKG_LICENSE_FILES
• Refresh patches

Applying ./patches/002-remove-buildtime-module-install using plaintext: 
patching file CMakeLists.txt
Hunk #1 succeeded at 310 (offset 7 lines).
Hunk #2 succeeded at 334 with fuzz 2 (offset 7 lines).

Applying ./patches/004-disable-sysrepod-autostart using plaintext: 
patching file src/clientlib/client_library.c

Applying ./patches/005-fix-struct-ucred-define using plaintext: 
patching file src/common/sr_utils.c
Hunk #1 succeeded at 477 (offset 17 lines).

• Use better URL

[neheb]

I have a similar pull request: #9491

I'm not sure how to proceed.

[neheb]

I think I’ll just merge and rebase the other one.