x86-64: slightly stream-line 32-bit syscall entry code

commit 295286a89107c353b9677bc604361c537fd6a1c0 upstream

x86-64: slightly stream-line 32-bit syscall entry code

[ required for following patch to apply properly ]

Avoid updating registers or memory twice as well as needlessly loading
or copying registers.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>