arm: fixed the ARM version of the routine __cr_restore_rt

This patch fixes a stack corruption caused by the routine
since it pushes the registers R4, R5, R6, and R7
onto the stack that results in a restorer crash
while restoring a zombie (https://bugzilla.openvz.org/show_bug.cgi?id=2663

)

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