x86: Remove now-unused save_rest()

b3af11afe06a ("x86: get rid of pt_regs argument of iopl(2)")
dropped PTREGSCALL which was also the last user of save_rest.
Drop that now-unused function too.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Link: http://lkml.kernel.org/r/1378546750-19727-1-git-send-email-bp@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>