sys-boot/netboot: bump to EAPI=7.

sys-boot/netboot: bump to EAPI=7.

Changes to ebuild:

* bumped from EAPI=2 to EAPI=7.
* license changed to GPL-2+, since GPL-2 is wrong here.
* added amd64 arch, as it compiles and works fine on this arch.
* Patched several makefiles, to install into the correct pathes.
* Overhauled whole build to make it more clean.
* Install more docs, to make it complete.
* Dropped unnecessary move/delete of directories/files.
* Added better description to ebuild and metadata.xml.
* Taking ownership.

Package-Manager: Portage-2.3.62, Repoman-2.3.12
Signed-off-by: Conrad Kostecki <conrad@kostecki.com>
Closes: https://github.com/gentoo/gentoo/pull/11575
Signed-off-by: Patrice Clement <monsieurp@gentoo.org>