cr-restore: prepare removing arch_export_unmap_compat for !CONFIG_COMPAT

We don't need __export_unmap_compat() for !CONFIG_COMPAT in restorer
blob. This preparation will allow to move compatible unmap that's
written in x86 asm from generic restorer blob to arch/x86.

Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>