This is to allow version-specific options to the list of defaults.
* gnu/packages/linux.scm (%default-extra-linux-options): Transform to...
(default-extra-linux-options): ... this procedure, which accepts a 'version'
argument.
(make-linux-libre, linux-libre-arm-generic, linux-libre-arm-generic-5.10)
(linux-libre-arm-generic-5.4, linux-libre-arm64-generic)
(linux-libre-arm64-generic-5.10, linux-libre-arm64-generic-5.4)
(linux-libre-riscv64-generic, linux-libre-mips64el-fuloong2e)
(linux-libre-with-bpf): Adjust accordingly.
* doc/guix-cookbook.texi (Customizing the Kernel): Adjust accordingly.
Change-Id: Ifd3be8b7ed8699bada224a938dbc84205366ff3d