cr: generalized the prototype of the routine restore_fpu()

A struct sigframe* instead of fpu_state_t should be passed
to the routine restore_fpu() since FPU registers are stored
in different fields of the sigframe in different architectures.
An architecture-specific implementation of the routine restore_fpu()
should know details of this layout instead of construct_sigframe().

This change makes it possible to move ARM FPU restoration
from sigreturn_prep_fpu_frame() (where it caused a segfault
since the pointer fpu_stat has become invalid in the dumper
address space) to restore_fpu()

Signed-off-by: Alexander Kartashov <alekskartashov@parallels.com>
Acked-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>