sch: make separate copy of nvs.h

Change-Id: Ie3a843a76ebf9f5d825e14c4359fb3ecaa052e38
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/6809
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>