Enforce E501: Limit the line length to 79 for files in pmb/parse - part 1

Made changes to limit the line length in following files for #1986 (closed),

• pmb/parse/_apkbuild.py
• pmb/parse/apkindex.py
• pmb/parse/binfmt_info.py
• pmb/parse/deviceinfo.py
• test/test_parse_apkbuild.py

Added the above files in E501 flake8 command list. Substitute f-string for string concatenation.