mkinitrd: add explicit GPLv2+ license

The only reference to the license right now is the
spec file, lets make the license even more obvious
for things not scraping for SPDX files.

Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
mkinitrd: embrace the Developer Certificate of Origin for contributions

The Linux kernel started to embrace a light weight development contribution
agreement process called the Developer Certificate of Origin (DCO) circa
2004. Attorneys all over the planet have conferred a lot of respect and
appreciation for this document and it provides a light weight alternative to
cumbersome and controversial Contribution License Agreements (CLAs).

Similar to streamlining FOSS licenses we also all stand to gain from
streamlining a light weight contribution agreement process for development
and in light of this the the Linux Foundation recently has made the DCO a
standalone project [0] so that any FOSS project under any FOSS license can
take advantage of the same gains. The motivation and intent is documented
only currently on my blog post [1].

Lets take advantage of the new shiny DCO and embrace it for contributions.

[0] http://developercertificate.org/
[1] http://www.do-not-panic.com/2014/02/developer-certificate-of-origin.html

Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
mkinitrd: add config to SUSE /sbin/installkernel

Without copying the config file anyone using SUSE who has installed
xen from source, and built their own kernel won't get xen picked up
by the perl-bootloader [0] update-bootloader. The requirement for the
config file comes from upstream grub2 /etc/grub.d/20_linux_xen [1] which
will only add xen as an instance to your grub.cfg if and only if it
finds in your config file either of:

CONFIG_XEN_DOM0=y
CONFIG_XEN_PRIVILEGED_GUEST=y

Without this a user compiling and installing their own kernel with
proper support for xen *and* with the xen hypervisor present will
not get update-bootloader to pick up the xen instance.

I've tested with both:

	1) sudo make modules_install install
        2) update-bootloader --refresh

1) was done using the latest Linux kernel sources after applying this
patch, and 2) was done by simply copying over manually the config file
manually.

[0] https://github.com/openSUSE/perl-bootloader
[1] http://git.savannah.gnu.org/cgit/grub.git/tree/util/grub.d/20_linux_xen.in

Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>