xen: x86: drop the ".gz" suffix when installing

xen: x86: drop the ".gz" suffix when installing

As Jan says it is pretty meaningless under /boot anyway. However I am slightly
concerned about breaking bootloaders (or more specifically their help scripts
which automatically generate config files). By inspection at least grub 2's
update-grub script (as present in Debian Wheezy) seems to cope (it matches on
xen* not xen*.gz)

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Keir Fraser <keir@xen.org>
Acked-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Jan Beulich <jbeulich@suse.com>