Since commit 22396f76 ("restore: construct sigframe in crtools")
sigframe is unused in restore_thread_common, as restore gpregs/fpu regs
now does construct_sigframe.

Impact: cleanup
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>