x86-64: Slightly shorten copy_page()
x86-64: Slightly shorten copy_page()

%r13 got saved and restored without ever getting touched, so
there's no need to do so.

Signed-off-by: Jan Beulich <01de09643e0ae62e116f8bd77de435799874b456@suse.com>
Cc: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>
Cc: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Link: 5e74eb73a9670aca634c68e846deacf06e272c74@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@elte.hu>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs